MediaProvider requires permissions that diverge from those
of a typical priv_app. This create a new domain and removes
Mtp related permissions from priv_app.

Bug: 33574909
Test: Connect with MTP, download apps and files, select ringtones
Test: DownloadProvider instrument tests, CtsProviderTestCases

Change-Id: I950dc11f21048c34af639cb3ab81873d2a6730a9