Subscriber Services: DHCPv6 requests that include a request for both DHCPv6 IA_NA and DHCPv6 prefix delegation

For DHCPv6 subscribers on DHCP access networks, a client can solicit both an IA_NA address and a prefix for DHCP prefix delegation, and the session comes up even if either the address or the prefix is not allocated. In earlier releases, an error was returned if the BNG did not return both an address for DHCPv6 IA_NA and a prefix for DHCPv6 prefix delegation.