fsperf: Fix missing request cases

If there is missing queue event (e.g. start fsperf in middle of test),
"complete" can't find pending IO.

So, if there is missing pending IO, this ignores those IO.

Signed-off-by: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
fsperf: Fix missing workqueue_execute_start cases

If there is missing "workqueue_execute_start" event (e.g. start fsperf
in middle of test), "workqueue_execute_end" can't find symbol of workfn.

So, if there is missing workqueue_execute_start, this ignores it.

Signed-off-by: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>