[MaaS] Override failed testing by default

[MaaS] Override failed testing by default

Some nodes fail automatic testing done by MaaS during commissioning,
although running the testing suites one more time manually works.
For now, just override all 'failed testing' nodes unconditionally.

[stable/euphrates cherry-pick additions]
Note: Since our salt formulas are pinned to 2017.12 repos, we
need to backport one salt-formula-maas patch merged upstream, which
adds support for translating status code '22' to 'Failed testing' [1].

JIRA: FUEL-333

[1] https://github.com/salt-formulas/salt-formula-maas/commit/08ffc3ff

Change-Id: I13d3ee3d82550524480aa53aa8752ab90aa940cd
Signed-off-by: Alexandru Avadanii <Alexandru.Avadanii@enea.com>
(cherry picked from commit 81561126307f15d4f65a743ed2431ea8c713a921)