Smack: Provide information for UDS getsockopt(SO_PEERCRED)

This patch is targeted for the smack-next tree.

This patch takes advantage of the recent changes for performance
and points the packet labels on UDS connect at the output label of
the far side. This makes getsockopt(...SO_PEERCRED...) function
properly. Without this change the getsockopt does not provide any
information.

Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>