This reverts commit e7b48c0b.

Support absolute and relative paths. Paths starting with "rbd:" are special,
and they point to the rbd endpoint, served by Ceph.

cache parameter is optional, in case if present, will be used as-is, even with
empty cache.

external-disk-number, external-disk-size and external-disk-format has been
removed from the schema to become hidden, nevertheless it's expected to be
fully supported, as long tests are kept.

Loudly fail in case if old and new ways are used in the same time.

Thanks to recent increased test coverage python3 compatibility issue was
spotted, and can be fixed.

image-download-controller raises error state during download process, to
inform other components that download is not ready yet.

template-kvm-run.in asserts presence of all images and otherwise refuses to
start, so that it gives chance for the image to being downloaded.

Sorting images happen by proper key instead of needless links.

Fix race condition, as the hash parameter shall depend on boot image url
configuration, and not it's failure state.

The default virtio-net-pci is not supported by some legacy OSes, so allow
customize it, to provide such support.

This allows to synchronise server position of the mouse with the client one,
thus making mouse really usable.

See https://wiki.gentoo.org/wiki/QEMU/Options#USB

Thanks to minimising amount of changing parameters of the wrapper, by setting
RAM and CPU to "init" values, it's possible to not restart the wrapper in case
of device hotplugging in for changes of those parameters.

Note that this shows regressiong to enable-device-hotplug which happened
after upgrade to qemu 5.2.0 in 8dc22418.

slapos.toolbox is added in order to use qemuqmpclient.

This fixes 157dd7ab.

This will minimise amount of needless restarts.

Special care is taken to work with files appearing later, by preparing them as
empty ones.

Covered assets for parameter change are:
 * software release
 * boot-image-url-list
 * boot-image-url-select
 * virtual-hard-drive-url

For sanity virtual-hard-drive-md5sum became mandatory.

virtual-hard-drive-gzipped case is covered.

Given that the default is to use raw for device drives and qcow2 for
file drives,  and that 'discard' was already enabled for raw, this
commit is in practice mainly for file drives, for which QEMU processes
TRIM by punching holes (i.e. the image file becomes sparse).

This reduces disk usage not only by the process running the VM but
also by backups and replicas (e.g. runner1).

For qcow2 at least, the discarded space can be reused for other blocks
and qemu compacts the image at dump (for backups) so images on replicas
are not sparse.

When an image disk format doesn't support it, QEMU ignores the option
so it's safe.

Guest support of TRIM for virtio-blk is recent: Linux 5.0

The user must be aware of any mistake he did. For example, he may lose
time by not understanding why the VM does not behave as expected or by
distorting measures in benchmarks.

The only legitimate reason to automatically fix a parameter is backward
compatibility, if a value is not valid anymore. But such fallback
should only be temporary. There's no such case recently.

At last, it increased maintenance by having to keep the lists of valid
values up-to-date.

About:

  -  if disk_info['io'] == 'native':
  -    additional_disk_options += ',cache.direct=on'

These lines are redundant when cache is none.

The keyboard option is actually not recommended in the QEMU
documentation
(https://manpages.debian.org/buster/qemu-system-x86/qemu-system-x86_64.1.en.html).
After some tests, it appears that noVNC is already sending raw keyCode
to QEMU since 2016 (see
https://github.com/novnc/noVNC/commit/f4f4e8993d6daeb43b957766cd6973993232ba13).

More information can be found in
https://github.com/novnc/noVNC/issues/21 and
https://www.berrange.com/posts/2010/07/04/more-than-you-or-i-ever-wanted-to-know-about-virtual-keyboard-handling/

Use json to generate .slapos-disk-permission in a way, that devperm manager
will be able to consume it.

slapgrid is the old name of slapos node command.

This reverts commit cc1713c3.

Unfortunately a lot of installation OS ISOs (like Debian 9 and 10) do not
support such device during installation process, because of missing drivers
on the OS CD.

Also note the ISOs limitation in the advanced field.

By using virtio-scsi-pci it's possible to attach many CD-ROMs to be boot from.

Thanks to using to draft-06 schema oneOf the "Boot image" field provides a
list of images to select one to boot.

Downloadable images are enabled when key image-url-list (described in
instance-kvm-input-schema.json) is present.

Images are downloaded outside of partition processing, as this can take a lot
of time by template/image-download-controller.py

Configuration is checked and cleaned up by
template/image-download-config-creator.py

Promises are used for:

 * checking if the current configuration from the request has been processed
 * checking status of configuration generation, image download process and
   checksum validity

Details about errors are exposed by using monitor stack provided HTTP server,
so that user is able to take informed decision about how to fix the problem.

If there is IPv6 on both interface, Linux will put a default route on
ens3 preventing IPv6 to work correctly on ens4.
Even disabling totally IPv6 from inside the host on ens3 may not work.
It is safer to disable it from qemu process directly. Also, it will ease
the configuration of the host.

When the image is a block device, the guest must also run Linux >= 5.0.

otherwise it will stall VM execution.

This is observed inside qemu VM started by 

https://lab.nexedi.com/nexedi/slapos/blob/master/software/erp5testnode/testsuite/deploy-test/software.cfg

In qemu log one can see:
===
QEMU waiting for connection on: disconnected:unix:/srv/slapgrid/slappart6/var/qmp_socket,server

===

Affected version:

root@z600:/srv/slapgrid/slappart6# /opt/slapgrid/7903668a197f3cf8f94375d0739a21e8/parts/kvm/bin/qemu-system-x86_64 --version
QEMU emulator version 2.8.0
Copyright (c) 2003-2016 Fabrice Bellard and the QEMU Project developer

/reviewed-on nexedi/slapos!585

Close the NBD socket when testing it so it won't mess up qemu.

/reviewed-on nexedi/slapos!516

Set cache.direct=on when using native aio (needed by qemu)

/reviewed-on nexedi/slapos!399

/reviewed-on nexedi/slapos!380

  it  clean up....

  Up to some extent we would like to set diskcache=none and diskaio=native