SLING-4106 - adding exception handling for trigger (un)registration

git-svn-id: https://svn.apache.org/repos/asf/sling/trunk@1634858 13f79535-47bb-0310-9956-ffa450edef68
SLING-4106 - adding exception handling for trigger (un)registration

git-svn-id: https://svn.apache.org/repos/asf/sling/trunk@1634860 13f79535-47bb-0310-9956-ffa450edef68