LU-14606 llog: hide ENOENT for cancelling record

LU-14606 llog: hide ENOENT for cancelling record

Llog allows parallel records processing. A record could be cancelled
at callback. If two threads processing and cancelling the same record,
one thread would get ENOENT.
The error was observed during purging changlog records.The patch
adds reproducer test sanity 160m.

This is a valid case, let's hide ENOENT error from a caller.

HPE-bug-id: LUS-9826
Signed-off-by: Alexander Boyko <alexander.boyko@hpe.com>
Change-Id: Id00b959e6f329c2ad34966f8a17a52f71680f24c
Reviewed-on: https://review.whamcloud.com/43264
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Alexander Zarochentsev <alexander.zarochentsev@hpe.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>