OAK-2001 TarMk compaction can still cause repository growth
 - prevented ConcurrentModificationException by wrapping in an synchronized block

git-svn-id: https://svn.apache.org/repos/asf/jackrabbit/oak/trunk@1614596 13f79535-47bb-0310-9956-ffa450edef68
OAK-2000: Observation events accessibility not checked correctly
Trivial: rename constructor arg

git-svn-id: https://svn.apache.org/repos/asf/jackrabbit/oak/trunk@1614604 13f79535-47bb-0310-9956-ffa450edef68