CachedAppOptimizer: ensure binder is never frozen with app unfrozen

Unfreezing a binder interface after the app, as well as freezing it
before the app, opens a time window during wich the process is active
and yet synchrnous binder transactions would fail.

Unfreeze binder before the app, and similarly freeze it after freezing,
to ensure consistent states.

Bug: b/171239744
Test: verified correct working of the sequence by manually sending
synchronous messages during the critical intervals.

Change-Id: I5fad4cdf497a567aceb15b1fc3025b049c54983e