Adjust MTP to reference by specific volume name.

The MediaStore.VOLUME_EXTERNAL volume is a merged view of all storage
devices, and clients working on a specific volume need to focus on
the volume they're interested in.

Bug: 129840030
Test: atest --test-mapping packages/providers/MediaProvider
Change-Id: I86596987a32f393580377e1dcf80ba28b0cae945
1 file changed