s4:kdc: Check authentication policy server restrictions

s4:kdc: Check authentication policy server restrictions

For a constrained delegation request, we need to pass ‘delegated_proxy’
(and the delegated proxy PAC, if one was provided) into
samba_kdc_update_pac() so that we can verify that the delegating server
is allowed to authenticate to the target server.

The ‘const’ is entirely unnecessary in a function declaration, but we
add it just to be consistent.

Signed-off-by: Joseph Sutton <josephsutton@catalyst.net.nz>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>
Reviewed-by: Stefan Metzmacher <metze@samba.org>