Change creation of AlarmUpdatedEvent and AlarmDeletedEvent

Threshold Engine needs the sub alarm id and the alarm sub expression
they map to for AlarmUpdatedEvent and AlarmDeletedEvent

Add new method to AlarmMySqlRepositoryImpl to get the sub alarm info
from the sub_alarm table. Thresh creates the entries in the sub_alarm
table

Fix the AlarmMySqlRepositoryImpl and AlarmDefinitionMySqlRepositoryImpl
unit tests

Send AlarmDeletedEvents for all alarms that get deleted when
an Alarm Definition is deleted

Add severity to the AlarmDefinitionUpdatedEvent

Change-Id: I61c887d5725a76faf3a2fd3b07a53a4f6275ed81
Merge "Change creation of AlarmUpdatedEvent and AlarmDeletedEvent"