Add test for DE (user) snapshot and restore.

This adds a test for rolling back device encrypted (user) apex data,
similar to the tests previously added for DE_sys and CE data.

Bug: 141148175
Test: atest StagedRollbackTest#testRollbackApexDataDirectories_DeUser
Change-Id: I632957449e4aa4f93df2e8bf0ae541937472d9fe
1 file changed