fix the deadlock bug for rpcCloseConn

src/rpc/src/rpcMain.c

@@ -287,7 +287,7 @@ void rpcClose(void *param) {
   (*taosCleanUpConn[pRpc->connType])(pRpc->udphandle);
 
   for (int i = 0; i < pRpc->sessions; ++i) {
-    if (pRpc->connList[i].user[0]) {
+    if (pRpc->connList && pRpc->connList[i].user[0]) {
       rpcCloseConn((void *)(pRpc->connList + i));
     }
   }
@@ -495,9 +495,10 @@ static void rpcCloseConn(void *thandle) {
   SRpcConn *pConn = (SRpcConn *)thandle;
   SRpcInfo *pRpc = pConn->pRpc;
 
+  if (pConn->user[0] == 0) return;
+
   rpcLockConn(pConn);
 
-  if (pConn->user[0]) {
   pConn->user[0] = 0;
   if (taosCloseConn[pConn->connType]) (*taosCloseConn[pConn->connType])(pConn->chandle);
 
@@ -522,7 +523,6 @@ static void rpcCloseConn(void *thandle) {
   pConn->pContext = NULL;
 
   tTrace("%s %p, rpc connection is closed", pRpc->label, pConn);
-  }
 
   rpcUnlockConn(pConn);
 }