feature(udf):start udfd can be disabled

source/libs/function/src/tudf.c

@@ -141,6 +141,7 @@ static void udfWatchUdfd(void *args) {
 int32_t udfStartUdfd(int32_t startDnodeId) {
   if (!tsStartUdfd) {
     fnInfo("start udfd is disabled.")
+    return 0;
   }
   SUdfdData *pData = &udfdGlobal;
   if (pData->startCalled) {

tests/script/tsim/query/udf.sim

@@ -3,6 +3,7 @@ system sh/stop_dnodes.sh
 system sh/deploy.sh -n dnode1 -i 1
 system sh/cfg.sh -n dnode1 -c wallevel -v 2
 system sh/cfg.sh -n dnode1 -c numOfMnodes -v 1
+system sh/cfg.sh -n dnode1 -c startUdfd -v 1
 
 print ========= start dnode1 as LEADER
 system sh/exec.sh -n dnode1 -s start