Improving the poller-test command to work better with advanced features.

The PSM requires to know the node's label in order to work with the
${nodelabel} placeholder for web-site monitoring. For this reason, the
implementation of the poller test has been updated to retrieve the
node's information from the database prior executing the poller test.
NMS-6395 handle optional perl dependencies more gracefully
Merge remote-tracking branch 'origin/1.12' into rc/stable/1.14.0

Conflicts:
	opennms-services/src/main/java/org/opennms/netmgt/poller/MonitorTester.java