dhcpv6: T3262: don't run DHCPv6 client when only dhcpv6-options is configured
dhcpv6: T3262: don't run DHCPv6 client when only dhcpv6-options is configured

If dhcpv6-options is configured without requesting a DHCPv6 address or PD, the
dhcpv6pd variable is assigned an empty dict.

vyos/vyos-1x,vyos/vyos-1x,vyos/vyos-1x,vyos/vyos-1x