Don't throw when setting the same windowing mode

We may throw UnsupportedOperationException when setting windowing mode
other than fullscreen or unspecified in the locked task mode. However if
the container in question is already in the same mode there is no need
to fail the request.

Bug: 263492303
Test: Build and boot.
Change-Id: I55caa81b0c5a259ae39785c0ef473e12aa8b3286