[Bug] running txn number does not equals to the real running txn number.

**Describe the bug**
The result of `SHOW PROC "/transactions/dbId"` shows there are, for example, 22 running
transactions. But the result of `SHOW PROC "/transactions/dbId/running"` is empty.

And because of this, if the running txn number is higher than config `max_running_txn_num_per_db`, user can not submit load job.
