Also adapt build.sh for bootstrapping with python3.

This is a fixup of 4b28ab13. See also nexedi/slapos!1154

Instead of dropping some keys (easy to implement, impossible to test and easy
to leak) create whitelist of passed keys of slaves to the nodes.

Then if there are new keys in slave's connection parameters the nodes are
protected against being polluted with them.

Needed for `six` to avoid such message on:
  + from past.builtins import cmp
    => Redefining built-in 'cmp' (redefined-builtin)
  + from six.moves import xrange
    Redefining built-in 'xrange' (redefined-builtin)

Python2 already provides __code__ and __defaults__ so this just does the same on
PythonScript.

This default prevented extending the section with `inline` option
because `inline` and `url` conflict. This was not a problem when
the deprecated `template` or `template = inline:` option was used.

Setting `url = < nothing >` does not resolve the conflict currently.

Since all section that extend `jinja2-template` set their own `url`
or `inline`, the default value was never used anyway.

The default `filename` option is also no longer needed.

See merge request nexedi/slapos!1139

This software extends an old software, so we can not apply changes
that need a new version of slapos.recipe.template at this point.

By changing jinja2-template users from overriding url= to defining
template= the original url= option was expanded, but this failed
because there is no filename=. Define a default filename to prevent
this.

This fixes errors like for example:

    While:
      Installing.
      Getting section instance.cfg.
      Initializing section instance.cfg.
      Getting option instance.cfg:url.
    Error: Referenced option does not exist: instance.cfg filename

when installing component/pygolang/test.cfg

Revert "stack/ndtest,software/erp5testnode/testsuite: partially revert f5ebda78"

This reverts commit 90f29b1a and
subsequent fixups.

This partial revert was made in a rush without clear understanding
of the problem. Reverting the partial revert to apply proper fixes.

fixup! stack/ndtest,software/erp5testnode/testsuite: partially revert f5ebda78

fixup! stack/ndtest,software/erp5testnode/testsuite: partially revert f5ebda78

stack/ndtest,software/erp5testnode/testsuite: partially revert f5ebda78

These were actually :jinja2 versions of the recipe, so we can not
change them like this.

This commit was made in a rush to repair tests failing in loop, there
might still be mistakes.

Remove existing "embedded instance" options:
- `embedded-sr`
- `embedded-sr-type`
- `embedded-instance-parameters`

Instead introduce `one-time-embedded-instance` option:
- Only taken into account when Theia is instantiated the first time.
- Content should be a JSON object with:
  - 'software-url': string of the software URL
  - 'software-type': (optional) string of the software type
  - 'instance-parameters': (optional) JSON object

If the option is non-empty:
- Theia will attempt once to:
  - Parse the JSON content
  - Create a supply/request script
  - Call the script
- A promise will check whether the script was successfully called.

If the promise fails forever, e.g. because of ill-formed JSON, emptying
the option will remove the promise. Editing the option after the first
time will have no effect, whether the promise succeded or not.

Use slapos.recipe.template instead of slapos.recipe.template if possible

Harmonize template keys :
rendered -> output
template -> url
template = inline: -> inline =

Delete "mode" key

See merge request !1151

The egg slapos.core is now used with python3 by default (except in slaprunner).

See merge request nexedi/slapos!1154

slaprunner is actually not working in python3 (see
nexedi/slapos.toolbox!103)
and is currently unmaintained.

theia, erp5testnode are both running a slapos standalone. We don't
change slaprunner to python3 because it's not maintained anymore and
should disappear in the near future.

After removal of git server in f3dc178f,
no need for mod_cgid anymore.

Also, the mod_cgid was reporting an error because ScriptSock was not set
so the socket file was created in the software compilation folder:

[cgid:error] [pid 109996:tid 139713924945728] (13)Permission denied: AH01243: Couldn't bind unix domain socket /srv/slapgrid/slappart71/srv/runner/shared/apache/81977b7512b75d38df008fc5ede74d94/logs/cgisock.105061

Use the exact version number displayed on the pypi index, because our shacache system is based on the URL which contains a package version number.

See merge request nexedi/slapos!1134