Protect sensitive service operations.

Also explicitly attach volume before scanning it.

Bug: 117932814
Test: atest MediaProviderTests
Test: atest cts/tests/tests/media/src/android/media/cts/MediaScanner*
Test: atest cts/tests/tests/provider/src/android/provider/cts/MediaStore*
Change-Id: I04e61c8a92020b6c2bce904419f7e764e9e21298
5 files changed