roll: make sure unlinked inodes before orphans.

roll: make sure unlinked inodes before orphans.

If we find an unlinked inode during roll-forward it should end up
being an orphan.
But we don't look at the orphan file soon enough, and if it isn't in
the orphan file then we can BUG, which is bad.
So if we do find one, make it an orphan.  If it turns out to be in the
orphan file that entry will just be discarded.

Signed-off-by: NeilBrown <neilb@suse.de>