apparmor: make sure unix socket labeling is correctly updated.

apparmor: make sure unix socket labeling is correctly updated.

When a unix socket is passed into a different confinement domain make
sure its cached mediation labeling is updated to correctly reflect
which domains are using the socket.

Fixes: c05e705812d1 ("apparmor: add fine grained af_unix mediation")
Signed-off-by: John Johansen <john.johansen@canonical.com>