NFSv4: Schedule recovery if nfs40_walk_client_list() is interrupted

If a timeout or a signal interrupts the NFSv4 trunking discovery
SETCLIENTID_CONFIRM call, then we don't know whether or not the
server has changed the callback identifier on us.
Assume that it did, and schedule a 'path down' recovery...
Tested-by: Steve Dickson <steved@redhat.com>
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>

fs/nfs/nfs4client.c

@@ -531,6 +531,13 @@ int nfs40_walk_client_list(struct nfs_client *new,
 			*result = pos;
 			dprintk("NFS: <-- %s using nfs_client = %p ({%d})\n",
 				__func__, pos, atomic_read(&pos->cl_count));
+			goto out;
+		case -ERESTARTSYS:
+		case -ETIMEDOUT:
+			/* The callback path may have been inadvertently
+			 * changed. Schedule recovery!
+			 */
+			nfs4_schedule_path_down_recovery(pos);
 		default:
 			goto out;
 		}