BUG/MINOR: cli: do not perform an invalid action on "set server check-port"

The "set server <srv> check-port" CLI handler forgot to return after
detecting an error on the port number, and still proceeds with the action.
This needs to be backported to 1.7.
diff --git a/src/server.c b/src/server.c
index c96b096..3265680 100644
--- a/src/server.c
+++ b/src/server.c
@@ -4155,11 +4155,15 @@
 			appctx->ctx.cli.severity = LOG_ERR;
 			appctx->ctx.cli.msg = "'set server <srv> check-port' expects an integer as argument.\n";
 			appctx->st0 = CLI_ST_PRINT;
+			SPIN_UNLOCK(SERVER_LOCK, &sv->lock);
+			return 1;
 		}
 		if ((i < 0) || (i > 65535)) {
 			appctx->ctx.cli.severity = LOG_ERR;
 			appctx->ctx.cli.msg = "provided port is not valid.\n";
 			appctx->st0 = CLI_ST_PRINT;
+			SPIN_UNLOCK(SERVER_LOCK, &sv->lock);
+			return 1;
 		}
 		/* prevent the update of port to 0 if MAPPORTS are in use */
 		if ((sv->flags & SRV_F_MAPPORTS) && (i == 0)) {