Fix route instance destroyed on route-stops -> route-edit nav

When a $resource instance method such as $update() is used,
the instance is resolved with the response from the server,
regardless of what that response is. So when scala API returns
text 'OK', our route object is destroyed. Quickfix is to use
the $resource class method instead.
Merge pull request #559 from WorldBank-Transport/feature/fix-route-back

Fix route instance destroyed on route-stops -> route-edit nav