Foreman Maintain

Fix intermittent test failures

Advanced run command and tests

Support for run_once procedures and repositories setup

Rollback support if the upgrade fails soon enough

Support for scenario serialization/deserialization

Extract control flow of upgrades to special file

Don't continue with scenarios when last is not finished

Introduce run_strategy for scenarios

Health-check scenarios are better to run all steps regardless of errors
(:fail_slow strategy), while the migration scenarios should fail as soon
as first failure happens (:fail_fast strategy).

By default, the scenarios are treated as `:fail_fast`.

Add --whitelist option

Allows to mark some steps to be ignored in the results: allows to
continue even when some checks are failing.

Full upgrade scenario

This commit intoroduces more structured upgrade scenario consisting of
this scenarios:

• pre_upgrade_check - non-modifying checks: is the system ready?
• pre_migrations - modifying procedures before source update
• migrations - source update and main migrations...