revert code

src/client/src/tscServer.c

@@ -1999,8 +1999,7 @@ int tscProcessUseDbRsp(SSqlObj *pSql) {
   return 0;
 }
 
-int tscProcessDropDbRsp(SSqlObj *pSql) {
-  pSql->pTscObj->db[0] = 0;
+int tscProcessDropDbRsp(SSqlObj *UNUSED_PARAM(pSql)) {
   taosCacheEmpty(tscCacheHandle);
   return 0;
 }