A user reported an error where if we try to balance an fs after a device has
been removed it will blow up.  This is because we get an EIO back and this is
where BUG_ON(ret) bites us in the ass.  To fix we just exit.  Thanks,
Reported-by: NAnand Jain <Anand.Jain@oracle.com>
Signed-off-by: NJosef Bacik <josef@redhat.com>
Signed-off-by: NChris Mason <chris.mason@oracle.com>