Migrate default app data on non-FBE devices.

When a system app requests "forceDeviceEncrypted" they expect their
default app storage to point at a consistent location regardless of
device FBE support.  So when booting upgraded non-FBE devices, we
may need to migrate any data from CE to DE.  Note that on non-FBE
devices these are just semantic locations with identical protection.

This migration *only* works for non-FBE devices; changing
forceDeviceEncrypted flags on an FBE device always requires a full
data wipe.

Bug: 26668510
Change-Id: I8bd5b8ba882e6bd067c0381041b27c35d6e47788