Fixing NMS-6092: Syslog Northbounder is not translating the node labels

1) Updated NodeDaoHibernate to return null if an invalid nodeId is
passed to getLabelForId, to avoid IndexOutOfBoundsException.
2) Updated SyslogNorthbounder to use the nodeId from the alarm if the
alarm is associated with a node.
NMS-6093 Requisition ReST Caching Does Not Flush On Shutdown
Merge remote-tracking branch 'origin/1.12'

Conflicts:
	opennms-dao/src/main/java/org/opennms/netmgt/dao/hibernate/NodeDaoHibernate.java
	opennms-webapp/src/main/java/org/opennms/web/rest/RequisitionAccessService.java