MediaPlayer2: Remove libdrmframework.so dependency.

libdrmframework.so is being used in FileSource and MediaHTTP
for Forward Lock DRM use case.
This change removes this dependency from MediaPlayer2 by adding
ClearFileSource and ClearMediaHTTP.
Forward Lock DRM use case will be covered by MediaPlayer1.

Test: build & MediaPlayerTest & DrmTest
Bug: 111406958
Change-Id: I5cf51b2d6f477e8fa8950ac931c0142491baa747