fix(mnd): coverity scan issues

source/dnode/mnode/impl/src/mndConsumer.c

@@ -864,6 +864,8 @@ static int32_t mndConsumerActionUpdate(SSdb *pSdb, SMqConsumerObj *pOldConsumer,
     if (!existing) {
       taosArrayPush(pOldConsumer->currentTopics, &addedTopic);
       taosArraySort(pOldConsumer->currentTopics, taosArrayCompareString);
+    } else {
+      taosMemoryFree(addedTopic);
     }
 
     // set status

source/dnode/mnode/impl/src/mndDump.c

@@ -629,7 +629,7 @@ void mndDumpSdb() {
   }
   taosWriteFile(pFile, pCont, contLen);
   taosWriteFile(pFile, "\n", 1);
-  taosFsyncFile(pFile);
+  UNUSED(taosFsyncFile(pFile));
   taosCloseFile(&pFile);
   tjsonDelete(json);
   taosMemoryFree(pCont);

source/dnode/mnode/impl/src/mndStream.c

@@ -722,8 +722,10 @@ static int32_t mndProcessCreateStreamReq(SRpcMsg *pReq) {
   mInfo("trans:%d, used to create stream:%s", pTrans->id, createStreamReq.name);
 
   mndTransSetDbName(pTrans, createStreamReq.sourceDB, streamObj.targetDb);
-  if (mndTrancCheckConflict(pMnode, pTrans) != 0) goto _OVER;
-
+  if (mndTrancCheckConflict(pMnode, pTrans) != 0) {
+    mndTransDrop(pTrans);
+    goto _OVER;
+  }
   // create stb for stream
   if (createStreamReq.createStb == STREAM_CREATE_STABLE_TRUE &&
       mndCreateStbForStream(pMnode, pTrans, &streamObj, pReq->info.conn.user) < 0) {