Detect that a category is hidden when following a redirect

At the moment, if you have a category on a page, and the category redirects
to another category which is hidden, VE does not mark it as hidden when
loading the page.

Change-Id: I9303838d36fbc1e2c0ed16b8bb0020bf52a6c211
Merge "Detect that a category is hidden when following a redirect"