[TD-3147] <fix>: support insert internal instead of insert rate.

src/kit/taosdemo/insert.json

@@ -35,7 +35,8 @@
 			"auto_create_table": "no",
 			"data_source": "rand",
 			"insert_mode": "taosc",
-			"insert_rate": 0,
+			"insert_interval": 0,
+            "num_of_records_per_req": 100,
 			"insert_rows": 100000,
 			"multi_thread_write_one_tbl": "no",
 			"number_of_tbl_in_one_sql": 1,