Removing duplicated action on AlarmSeverityChangeController.

The clearing operation must be done through WebAlarmRepository only. It
is not necessary to execute an SQL Update through AlarmFactory for the
exact same thing that WebAlarmRepository is doing.
Make AlarmDao.getNodeAlarmSummaries() returns all instances.

It is better to control de number of rows on the AlarmBoxController
instead of doing it at DAO level.