staging/lustre: fix 'program hangs' errors

Fix 'program hangs' defects found by Coverity version 6.5.1:
Missing unlock (LOCK)
Returning without unlocking.

Intel-bug-id: https://jira.hpdd.intel.com/browse/LU-3054
Lustre-change: http://review.whamcloud.com/5870
Signed-off-by: Sebastien Buisson <sebastien.buisson@bull.net>
Reviewed-by: Dmitry Eremin <dmitry.eremin@intel.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Signed-off-by: Peng Tao <tao.peng@emc.com>
Signed-off-by: Andreas Dilger <andreas.dilger@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/lustre/lnet/selftest/rpc.c

@@ -661,8 +661,10 @@ srpc_finish_service(struct srpc_service *sv)
 
 	cfs_percpt_for_each(scd, i, sv->sv_cpt_data) {
 		spin_lock(&scd->scd_lock);
-		if (!swi_deschedule_workitem(&scd->scd_buf_wi))
+		if (!swi_deschedule_workitem(&scd->scd_buf_wi)) {
+			spin_unlock(&scd->scd_lock);
 			return 0;
+		}
 
 		if (scd->scd_buf_nposted > 0) {
 			CDEBUG(D_NET, "waiting for %d posted buffers to unlink",