apparmor: fix apparmor mediating locking non-fs unix sockets

the v8 and earlier policy does not encode the locking permission for
no-fs unix sockets. However the kernel is enforcing mediation.

Add the AA_MAY_LOCK perm to v8 and earlier computed perm mask which will
grant permission for all current abi profiles, but still allow specifying
auditing of the operation if needed.

Link: http://bugs.launchpad.net/bugs/1780227


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