Output start_ts so that tracing requests that cannot be batched can be easier (#4665)
Output start_ts so that tracing requests that cannot be batched can be easier (#4665)

Signed-off-by: Breezewish <a3a422de9ee6740e0686b745435c2f95bb3fed6b@pingcap.com>
BusyJay/tikv,pingcap/tikv,c4pt0r/tikv,BusyJay/tikv,pingcap/tikv,BusyJay/tikv,BusyJay/tikv