This reverts commit b6f08b9e.

Because this promise is relaxed, it leads to situation, that slaves are not
prepared, and no more processing would be needed.

Most possibly much more advanced logic is required.

This revertion is created to store the finding.

The error is like:

======================================================================
FAIL: test_https_url (test.TestSlave)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/srv/slapgrid/slappart33/t/dwd/soft/5dab459bdda9e53f1db7e0d954b37126/parts/slapos-repository/software/rapid-cdn/test/test.py", line 4792, in test_https_url
    self.assertEqual(
AssertionError: b'---[25 chars]nMIIDKjCCAhKgAwIBAgIUXLVeJJwHEQDnyJAbiqOlk7qkN[1100 chars]--\n' != b'---[25 chars]nMIIDVzCCAj+gAwIBAgIUJ99OAJ5qFcT5shJYBLHmdHKFu[1162 chars]--\n't

Store certificates, as they are important for understanding assertions.

validate_frontend_configuration is exactly check_command_execute, so just use
it.

Replace trafficserver_cache_availability with check_command_execute which
has the same functionality.

The eventual message from trafficserver_cache_availability will be visible
anyway.

publish-failsafe-error-promise and promise-key-download-url-ready shall be
less reactive, as otherwise it results with constant problems detection on
the running cluster, by raising tickets. When those promises are less
sensitive it gives time for the cluster to stabilize.

Make it possible to mock any specific cron entry.

Those are candidates to be shared by some other place, like slapos testing.

See merge request nexedi/slapos!1693

Following advice from https://luajit.org/download.html use recent commit id,
but rely on github archive.

Drop obsoleted patch, enforce --with-shared-termcap-library

Also use directly archive with patches.

Changes:
 * use xz archive
 * stabilize patch name
 * update patch to current version