Ticket #514 - investigate connection locking
    
    https://fedorahosted.org/389/ticket/514
    Reviewed by: mreynolds,nhosoi (Thanks!)
    Branch: master
    Fix Description: There were two locks involved for every operation - a lock
    to protect the pblock queue and a lock and condition variable to protect
    the counter variable.  This fix consolidates them into a single lock/cv for
    the pblock queue and gets rid of the separate lock for the counter.  The
    queue structures have been cleaned up and renamed work_q and work_q_size.
    The worker threads wait for new work if not shutdown and the work_q is
    empty.  In addition, the timeout interval for the wait for the work_q cv
    has been changed to "infinite" instead of 10 seconds.
    Platforms tested: RHEL6 x86_64
    Flag Day: no
    Doc impact: Yes