'Finds the common replay between two volumes.
This assumes that one volume was replicated from the other. This
should return the most recent replay.
:param svolume: Source SC Volume.
:param dvolume: Destination SC Volume.
:return: Common replay or None.'

def find_common_replay(self, svolume, dvolume):

    if (svolume and dvolume):
        sreplays = self._get_replay_list(svolume)
        dreplays = self._get_replay_list(dvolume)
        for dreplay in dreplays:
            for sreplay in sreplays:
                if (dreplay['globalIndex'] == sreplay['globalIndex']):
                    return dreplay
    return None
