Fixes #6057/BZ1117469 - highlight active tab based on URL.

Highlight the active menu tab based on the current URL
rather than relying on the controller and action.  This
fixes a problem where top level menus that contain plugin
menu items were not being highlighted when active.

http://projects.theforeman.org/issues/6057
https://bugzilla.redhat.com/show_bug.cgi?id=1117469