Delete Android/media orphaned rows per userid

When a package running in a cloned user is uninstalled, Android/media
contents for owner user are deleted as well. Proper user context should
be used to check package info.

MediaProvider#onIdleMaintenance() keeps deleting rows of Android/media
orphaned contents even though the files exist. Added check for file
existence.

Bug: 210798157
Test: atest MediaProviderTests
Test: atest ScopedStorageHostTest#testClearPackageData
Change-Id: I36eeab53d251b56470e43b14207563806760b049
2 files changed