Added some synchronization between the thread that initialize the replica store and the init method. We should now not be able to sstore any modification before the store is ready (which may fix the DIRSERVER-1810 issue, hopefully)

git-svn-id: https://svn.apache.org/repos/asf/directory/apacheds/trunk@1486411 13f79535-47bb-0310-9956-ffa450edef68