NMS-7185: Fixing NPE errors when querying events with offset in ReST API

This fixes http://issues.opennms.org/browse/NMS-7185 where it clears
any orders, limit and offset clauses in the CriteriaBuilder in
EventsRestService:getEvents()

Applying the same fix for AlarmRestService:getAlarms() and
AlarmStatsRestService:getStats(final OnmsSeverity severity)
Merge pull request #173 from corey-hammerton/jira/NMS-7185

NMS-7185: Fixing NPE errors when querying events with offset in ReST API