generic: test setting and getting encryption policies

Several kernel bugs were recently fixed regarding the constraints
for setting encryption policies.  Add tests for these cases and a
few more.

Signed-off-by: Eric Biggers <ebiggers@google.com>
Reviewed-by: Eryu Guan <eguan@redhat.com>
Signed-off-by: Eryu Guan <eguan@redhat.com>
3 files changed