Fix race condition tests.

- on affected tests: add an extra pair of rules to workaround a deadlock scenario caused by the race condition tests themselves
[MSC-122] Fixing stability detection

 * do not decrement unstable services when adding problem or failed controller
 * always ensure unstableServices >= 0 invariant
 * introducing service controller 'stable' flag - to properly notify stability observers
 * refactoring getStabilityState() method
[MSC-122] various fixes
 * use asserts instead of exception throwing
 * fix real regression cause and remove useless 'stable' flag