Updates the rotation and dimensions even mirror view is not inflated yet

Root cause: When the mirror view is not inflated yet, window
magnification will not update its cached dimension values and
rotation even there is a configuration settings changed.
Solution: Not to early return if the mirror view is not inflated
when onConfigurationChanged

Bug: 167973318
Test: atest WindowMagnificationControllerTest
Change-Id: I87290d16f3a10e7b88e8960391b89188443dacc8