UBUNTU: SAUCE: apparmor: LSM stacking: switch from SK_CTX() to aa_sock()

UBUNTU: SAUCE: apparmor: LSM stacking: switch from SK_CTX() to aa_sock()

LSM: Infrastructure management of the sock security

changes apparmor to use aa_sock() instead of SK_CTX() but doesn't
update the apparmor unix mediation because that code is not upstream.
So make the change here instead of modifying the LSM patch.

Signed-off-by: John Johansen <john.johansen@canonical.com>
Acked-by: Andrea Righi <andrea.righi@canonical.com>
Signed-off-by: Seth Forshee <seth.forshee@canonical.com>