Fix status bar cast icon not updating

Change the listening in CastControllerImpl so that it will always
at least passive discovery when callbacks are added.  When discovering
is set this will switch to request discovery.  This allows the
status bar to catch disconnect callbacks when QS is not discovering.

Bug: 17555869
Change-Id: Id2a80b98f6c7ca7e6a4d0ff00315d10a109e8259
1 file changed