Ensure alarm rule conform to alarm type

Threshold_rule or combination_rule must be set to an Alarm object,
and they cannot be set at the same time.
Alarm's type must be one of threshold and combination.
Threshold_rule and combination_rule should be validated according alarm's
type.

Change-Id: I97bf82defeaf0dc1a0e897e10886fd736361041d
Closes-bug: #1288677
Merge "Ensure alarm rule conform to alarm type"