[TD-1786]<fix>: failure of taos_clos may cause core

src/rpc/src/rpcTcp.c

@@ -173,6 +173,9 @@ void *taosInitTcpServer(uint32_t ip, uint16_t port, char *label, int numOfThread
 static void taosStopTcpThread(SThreadObj* pThreadObj) {
   // save thread into local variable and signal thread to stop 
   pthread_t thread = pThreadObj->thread; 
+  if (!taosCheckPthreadValid(thread)) {
+    return;
+  }
   pThreadObj->stop = true;
   if (taosComparePthread(thread, pthread_self())) {
     pthread_detach(pthread_self());

src/sync/src/taosTcpPool.c

@@ -302,6 +302,9 @@ static SThreadObj *taosGetTcpThread(SPoolObj *pPool) {
 
 static void taosStopPoolThread(SThreadObj *pThread) {
   pthread_t thread = pThread->thread;
+  if (!taosCheckPthreadValid(thread)) {
+    return;
+  }
   pThread->stop = true;
   if (taosComparePthread(thread, pthread_self())) {
     pthread_detach(pthread_self());