dhcpv6: always trigger script update in case of IA updates

dhcpv6: always trigger script update in case of IA updates

Trigger a script update when IAs have been updated during a reply in reponse
to to either a renew/rebind.
This will make sure new IAs assigned by the DHCPv6 server are published via
a script update.

This covers the following scenario:
    -Prefix A is assigned by DHCPv6 server
    -Prefix A is renewed but the DHCPv6 server does not include prefix A in
    the reply but assigns a new prefix B.
    -Prefix B is published via the update script while renews for prefix A
    will still be sent

Signed-off-by: Hans Dedecker <dedeckeh@gmail.com>