Ticket 47449 - deadlock after adding and deleting entries
Bug Description: If multiple clients are each doing their own add/delete of the same entries,
the server will deadlock very quickly.
Fix Description: The server was not signaling an error when it failed to lock the parent
entry lock. I've checked add/mod/modrdn functions as well, and they do correctly
unlock the cache entry(this includes the old/new superior for modrdn).
https://fedorahosted.org/389/ticket/47449
Reviewed by: richm(Thanks!)
(cherry picked from commit 6bd78b323a7d6ddaefc2cb8245e4356fd02e97e1)