Fix screenshot failure with transcoding

We currently attempt to convert transcode fds to original fds inside
the platform media players. This causes screenshot
failures in ExifInterface. To mitigate, we only match published videos
in DCIM/Camera.

Bug: 173543930
Bug: 175831095
Test: atest FileUtilsTest#testConvertToModernFd
Test: Manual, tested by both taking a screenshot and video transcoding.

Change-Id: I4abba3d9d36e83c5a019b32793bd38fee81d5f75