The dm-crypt solution requires a kernel patch that won't be present in
the GKI kernel, while the new metadata encryption system in the GKI
kernel solves this problem in a much cleaner way.
Test: create private volume on Cuttlefish, setting property both ways.
Bug: 147814592
Change-Id: Ie02bd647c38d8101af2bbc47637f65845d312cea
