Avoid callback leak in ComplicationHostViewController

There is no reason to add the callback instead of just checking the
state when it is needed, since we don't need to respond to state
changes. This avoids the callback object leaking when new instances are
created.

Bug: 272019210
Test: atest ComplicationHostViewControllerTest
Change-Id: I91d798a8130199a27ad134b30240a9073501d7fb