Add test for file ownership updates.

If a legacy app races to create a file at the same location as
an app in scoped storage, we update the ownership to the legacy
app to prevent the app in scoped storage from being able to
observe writes made by the legacy app.

Test: atest LegacyStorageHostTest
Bug: 150507736

Change-Id: I98b1d7a2fa26c2ba59bdeed03168d537aeb818bf
Merged-In: I98b1d7a2fa26c2ba59bdeed03168d537aeb818bf
(cherry picked from commit 9ba7fd65128df3dd2b399db873e4bc1870d36963)
4 files changed