service_dhcp_edit.php fixes from code inspection
service_dhcp_edit.php fixes from code inspection

To save you some time in testing and fixing, here are the bugs I noticed by code inspection.
dennypage/pfsense,NewEraCracker/pfsense,dennypage/pfsense,brunostein/pfsense,NewEraCracker/pfsense,ptorsten/pfsense,phil-davis/pfsense,ptorsten/pfsense,pfsense/pfsense,NewEraCracker/pfsense,jxmx/pfsense,pfsense/pfsense,phil-davis/pfsense,pfsense/pfsense,ch1c4um/pfsense,BlackstarGroup/pfsense,ptorsten/pfsense,jxmx/pfsense,NOYB/pfsense,pfsense/pfsense,phil-davis/pfsense,dennypage/pfsense,BlackstarGroup/pfsense,NewEraCracker/pfsense,ch1c4um/pfsense,dennypage/pfsense,phil-davis/pfsense,ch1c4um/pfsense,BlackstarGroup/pfsense,brunostein/pfsense,BlackstarGroup/pfsense,ch1c4um/pfsense,NOYB/pfsense,NOYB/pfsense,jxmx/pfsense,brunostein/pfsense