expensive_query doen't show cop information

## Bug Report

Please answer these questions before submitting your issue. Thanks!

### 1. Minimal reproduce step (Required)

### 2. What did you expect to see? (Required)
All copr message should be in expensive_query like the following:
`
2022-10-15 19:56:41 [2022/10/15 11:56:41.720 +00:00] [WARN] [expensivequery.go:188] [expensive_query] [cost_time=60.033688983s] [cop_time=16.732085333s] [request_count=xxx] [num_cop_tasks=xxx] [process_avg_time=0s] [process_p90_time=0s] [process_max_time=0s] [process_max_addr=xxx] [wait_avg_time=0s] [wait_p90_time=0s] [wait_max_time=0s] [wait_max_addr=xxx] [stats=xxx] [conn_id=xxx] [user=xxx] [database=xxx] [txn_start_ts=xxx] [mem_max="0 Bytes (0 Bytes)"] [sql="SOME BIG QUERY"]
`
### 3. What did you see instead (Required)
No copr message appears, we don't know which store this query runs on.
`
2022-10-16 16:26:36 [2022/10/16 08:26:36.535 +00:00] [WARN] [expensivequery.go:188] [expensive_query] [cost_time=60.050066623s] [stats=xxx] [conn_id=xxx] [user=xxx] [database=xxx] [txn_start_ts=xxx] [mem_max="0 Bytes (0 Bytes)"] [sql="SOME BIG QUERY"]
`
### 4. What is your TiDB version? (Required)
master