[TD-4238]<fix>: taosdemo async subscribe.

src/kit/taosdemo/async-sub.json

+{
+  "filetype": "subscribe",
+  "cfgdir": "/etc/taos",
+  "host": "127.0.0.1",
+  "port": 6030,
+  "user": "root",
+  "password": "taosdata",
+  "databases": "test",
+  "specified_table_query": {
+    "concurrent": 1,
+    "mode": "async",
+    "interval": 1000,
+    "restart": "yes",
+    "keepProgress": "yes",
+    "resubAfterConsume": 10,
+    "sqls": [
+      {
+        "sql": "select avg(col1) from meters where col1 > 1;",
+        "result": "./subscribe_res0.txt"
+      },
+      {
+        "sql": "select avg(col2) from meters where col2 > 1;",
+        "result": "./subscribe_res2.txt"
+      }
+    ]
+  },
+  "super_table_query": {
+    "stblname": "meters",
+    "threads": 1,
+    "mode": "sync",
+    "interval": 1000,
+    "restart": "yes",
+    "keepProgress": "yes",
+    "sqls": [
+      {
+        "sql": "select col1 from xxxx where col1 > 10;",
+        "result": "./subscribe_res1.txt"
+      }
+    ]
+  }
+}