Fix editing saving dhcp6prefixonly state
Fix editing saving dhcp6prefixonly state

Reported in redmine #3097 and forum http://forum.pfsense.org/index.php/topic,64483.msg350255.html#msg350255
ptorsten/pfsense,pfsense/pfsense,ch1c4um/pfsense,ptorsten/pfsense,dennypage/pfsense,ch1c4um/pfsense,pfsense/pfsense,NewEraCracker/pfsense,ch1c4um/pfsense,NewEraCracker/pfsense,ch1c4um/pfsense,jxmx/pfsense,jxmx/pfsense,jxmx/pfsense,phil-davis/pfsense,phil-davis/pfsense,pfsense/pfsense,pfsense/pfsense,brunostein/pfsense,ptorsten/pfsense,BlackstarGroup/pfsense,NewEraCracker/pfsense,dennypage/pfsense,brunostein/pfsense,dennypage/pfsense,phil-davis/pfsense,BlackstarGroup/pfsense,BlackstarGroup/pfsense,phil-davis/pfsense,NOYB/pfsense,brunostein/pfsense,NOYB/pfsense,NOYB/pfsense,NewEraCracker/pfsense,BlackstarGroup/pfsense,dennypage/pfsense