glusterd: Fixed spurious wakeups in glusterd syncops

glusterd syncops perform a barrier_wake whenever rpc_clnt_submit returned -1.
This is based on the wrong assumption that the cbkfn wasn't called.
This would result in one more wakeup than there ought to be.

Change-Id: I591e67c267f0e26d1145bf8fb5feeb2c13a751a1
BUG: 948686
Signed-off-by: Krishnan Parthasarathi <kparthas@redhat.com>
Reviewed-on: http://review.gluster.org/4802
Reviewed-by: Jeff Darcy <jdarcy@redhat.com>
Tested-by: Gluster Build System <jenkins@build.gluster.com>