o Exposed the lockWrite() and unlockWrite() methods in OperationManager
o Protected the backend in the syncWorker thred, by using the OperationManager lock, otherwise we may have some concurrent modification in JDBM
o Flushed the JDBM journal in the sync() method, otherwise the *.db file remain empty.

git-svn-id: https://svn.apache.org/repos/asf/directory/apacheds/trunk@1448166 13f79535-47bb-0310-9956-ffa450edef68