Fix a bug in Activity Up navigation dispatching

Propagate the return value from onNavigateUp as the result of
onMenuItemSelected. This fixes a bug where the action bar Up nav
button clicks would not be propagated to support lib FragmentActivity
or other activity subclasses that rely on processing otherwise
unhandled onMenuItemSelected events.

Change-Id: Id879dd1756ed06b8a7b720ebf0eae2a8ddc66ca8