Fix for hosed end-of-run log numbers

Fix for hosed end-of-run log numbers

For queued IO workloads, we complete the pending count in one
go at the end of the run. But the completion time isn't updated,
so we end up getting a lot of tail log entries that are identical
if the timing is against us.

Fix this by only accounting the first of the last batch of ios.

Signed-off-by: Jens Axboe <axboe@kernel.dk>