MediaFrameworkTest: compare media type only for supported media check

This is a CL to fix media test that is needed to 
ensure the local media playback works. 
This doesn't affect any OC feature.

Bug: 36699113
Test: adb shell am instrument -w -r -e class com.android.mediaframeworktest.stress.MediaPlayerStressTest com.android.mediaframeworktest/.MediaPlayerStressTestRunner
Change-Id: If1200e7f9a8c734b07f3f2a0420b3942920c948b
(cherry picked from commit 09fc83c8)