1) We're compacting tags on every deletion which is slow. Since we delete
albums in batch, we should just do one tag compaction at the end. Fixes
#1487.
2) Issue introduced in 3d952f41c8 where
we trigger an item_related_update in tag::clear_all(). Since
tag::clear_all() is called when we delete an item, this causes
the search module to attempt to index a deleted item. Move that
triggering upstream.