Better handling of upward recursive empty index deletion.

Better handling of upward recursive empty index deletion.

When an empty index blocks makes the parent empty, we recurse
up.
When we do that, we need to again perform the check for there
being children, and for this being an InoIdx block.
So jump further back, and tidy up the exit path to ensure we still
unlock properly.

This makes the extra check for InoIdx pointless.

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