[TD-3192] <feature>: support childtable limit and offset.

make insert.json back to early version.

src/kit/taosdemo/insert.json

@@ -34,14 +34,12 @@
         "super_tables": [{
             "name": "stb",
             "child_table_exists":"no",
-			"childtable_count": 100,
+            "childtable_count": 10000,
             "childtable_prefix": "stb_",
             "auto_create_table": "no",
             "data_source": "rand",
             "insert_mode": "taosc",
-            "childtable_limit": 33,
-            "childtable_offset": 33,
-			"insert_rows": 1000,
+            "insert_rows": 100000,
             "multi_thread_write_one_tbl": "no",
             "number_of_tbl_in_one_sql": 0,
             "rows_per_tbl": 100,