Revert "Allow holders of WRITE_MEDIA_STORAGE to write to secondary external storage"

This reverts commit b4171e508d37622774363d90bef16d76386eb44a.

Change-Id: I24bdb75c248f5ff465e77979cb7e6505dd721594
Signed-off-by: Josue Rivera <prbassplayer@gmail.com>
MediaProvider: allow write access to external SD

Without this, Gallery cannot delete photos on external SD.

Change-Id: Ifbebcdb167cca92a5a05158fa4c8b81512b77ba6