apparmor: add mediation class information to auditing

apparmor: add mediation class information to auditing

Audit messages currently don't contain the mediation class which can
make them less clear than they should be in some circumstances. With
newer mediation classes coming this potential confusion will become
worse.

Fix this by adding the mediatin class to the messages.

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