apparmor: fix nnp subset test for unconfined

The subset test is not taking into account the unconfined exception
which will cause profile transitions in the stacked confinement
case to fail when no_new_privs is applied.

This fixes a regression introduced in the fix for
https://bugs.launchpad.net/bugs/1839037

BugLink: https://bugs.launchpad.net/bugs/1844186


Signed-off-by: John Johansen <john.johansen@canonical.com>