Reinitialize cyclic barrier only once per cycle

    It was done for all threads syncing on a barrier. The one reaching the limit but
    also all waiting threads. So it could be reset by a thread while others have
    already started another round, leading to an deadlock (because some increments
    will be lost then).

    Now, cyclic barrier is reset for a new round by the thread reaching the limit
    and only this one.

Author: Christopher Faulet <cfaulet@haproxy.com>