Ticket 47759 - Crash in replication when server is under write load
    
    Bug Description:  When the server is under alot of load, a race condition allows
                      a replication connection LDAP struct to be freed(unbind) while
                      it is being used by another thread.  This leads to a crash.
    
    Fix Description:  Extend the connection lock to also cover ldap client interaction
                      (e.g. conn->ld struct).
    
    https://fedorahosted.org/389/ticket/47759
    
    Reviewed by: nhosoi & rmeggins(Thanks!!)
    (cherry picked from commit 9940ca29ca258891c52640a23adc2851afe59d0e)
    (cherry picked from commit 0e576c85c34826c4d63d9578db55f8179b4a1a60)
    (cherry picked from commit 2a80b7152823ca16628c2da48614166b8d2104a4)