Allow mkfs on device-mapper devices.

When running a GSI as a live image, a temporary userdata partition is
mounted through device-mapper. In order to properly format+encrypt this
like a normal userdata partition, mkfs must have rw permissions.

Bug: 122850122
Test: manual test
Change-Id: I5aa888f12a85954a9818ed04009832d76c139862
1 file changed