This adds a test for an I/O error during snapshot deletion, and maybe
more importantly, for how to repair the resulting image.  If the
snapshot has been deleted before the error occurs, the only negative
result will be leaked clusters -- and those should be repairable with
qemu-img check -r leaks.
Signed-off-by: NMax Reitz <mreitz@redhat.com>
Reviewed-by: NEric Blake <eblake@redhat.com>
Message-id: 20180509200059.31125-3-mreitz@redhat.com
Signed-off-by: NMax Reitz <mreitz@redhat.com>