* changed ptlrpc_unregister_reply(), ptlrpc_unregister_bulk() and

      ptlrpc_abort_bulk() to always l_wait_event() after doing
      PtlMDUnlink() on the relevant MD.  Previous code assumed that when
      PtlMDUnlink() returned PTL_MD_INVALID, the relevant callback handler
      must have run already, which isn't true for liblustre.  The
      l_wait_event() will be a NOOP for kernel lustre (condition already
      true) but gives the liblustre event handler a chance to call all
      the callbacks.