add dhcp6.name-servers option with DHCPD-PD regardless of PD length
add dhcp6.name-servers option with DHCPD-PD regardless of PD length

The existing code only includes a v6 name server IP in the
automatically generated dhcpdv6 configuration for tracking interfaces if
there are additional prefixes that can be delegated on to the next
router (i.e., if PD length > 2). The correct behavior is for this option
to be included regardless of the PD length, as implemented in this
change.

dennypage/pfsense,NewEraCracker/pfsense,jxmx/pfsense,BlackstarGroup/pfsense,NewEraCracker/pfsense,NOYB/pfsense,ch1c4um/pfsense,NOYB/pfsense,dennypage/pfsense,brunostein/pfsense,NewEraCracker/pfsense,dennypage/pfsense,ptorsten/pfsense,ptorsten/pfsense,NewEraCracker/pfsense,brunostein/pfsense,jxmx/pfsense,jxmx/pfsense,dennypage/pfsense,ptorsten/pfsense,NOYB/pfsense,ch1c4um/pfsense,phil-davis/pfsense,ch1c4um/pfsense,phil-davis/pfsense,brunostein/pfsense,pfsense/pfsense,pfsense/pfsense,phil-davis/pfsense,pfsense/pfsense,phil-davis/pfsense,pfsense/pfsense,BlackstarGroup/pfsense,BlackstarGroup/pfsense,ch1c4um/pfsense,BlackstarGroup/pfsense