Part of media security hardening MediaDrm was temporarily allowed to run in either mediaserver or mediadrmserver while all nexus devices were implementing support for the native_handle representation of secure buffers. Now that all nexus devices support native_handle, the MediaDrm stack can be removed from mediaserver. b/22990512 Change-Id: I96a5222f94cd1580ac411de5b48beb44b99cc8d7