Migrated away from view detaching as a signal

Previously the seekbar update stopped pretty much
immediately since the Lifecycle was set to destroyed
whenever detatched.
We're now listening whenever a view exists.
Similarly, were we making the view inactive whenever
reattaching, which happens constantly now

Test: add any player, observe progress bar updating
Bug: 154137987
Change-Id: I5bac0822ceb282999db35c797d7355127b1daf31