Turn screen on when testing with MediaRouter2TestActivity

This CL fixes test failures when screen is off.

Bug: 175701839, Bug: 176400886
Test: While screen is off, run:
      atest android.media.cts.MediaRouter2Test \
            android.media.cts.MediaRoute2ProviderServiceTest
Change-Id: I1b17b985dc9b449ac75a90c0f0cc05497c28fdfa
1 file changed