Fixes #6175 BZ1102951: Worked on updating content hosts details

Fixed a bug where content host details weren't be updated after adding or
removing a subscription. The status would still indicate invalid/valid
(respectively). I had to use $parent here as updating $scope.contentHost for
some reason did not update the webpage.
Merge pull request #4254 from daviddavis/update-system-info-subs

Fixes #6175 - Update content host info after adding/removing sub