xfs: EIO error handling test

xfs: EIO error handling test

Besides fail_at_unmount, all EIO error handling can stop umount
hanging on IO error too.

This case test EIO/max_retries and EIO/retry_timeout_seconds as
below:

1) fail_at_unmount=0 && \
   EIO/max_retries=1 && \
   EIO/retry_timeout_seconds=0

2) fail_at_unmount=0 && \
   EIO/max_retries=-1 && \
   EIO/retry_timeout_seconds=1

Make sure when fail_at_unmount=0, umount won't hang there.

Signed-off-by: Zorro Lang <zlang@redhat.com>
Reviewed-by: Eryu Guan <eguan@redhat.com>
Signed-off-by: Eryu Guan <eguan@redhat.com>