Fix too much recursion error during update_location_tree. Don't traverse...

... descendents during the all-locations update. Actually disable update_location_tree during prepopulate. Add tests for update_location_tree.
Done: 
https://github.com/nursix/eden/commit/7851e1c38921f2143ca9c6a29e136fab3d8795bb#diff-4698c71cdce0a53d1ea8731073f7fe6eR269