iotests: add busy/recording bit test to 124

This adds a simple test that ensures the busy bit works for push backups,
as well as doubling as bonus test for incremental backups that get interrupted
by EIO errors.

Recording bit tests are already handled sufficiently by 236.

Signed-off-by: John Snow <jsnow@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Tested-by: Eric Blake <eblake@redhat.com>
Message-id: 20190223000614.13894-11-jsnow@redhat.com
Signed-off-by: John Snow <jsnow@redhat.com>
2 files changed