Fix redmine #6640 DHCPv6 server time format
Fix redmine #6640 DHCPv6 server time format

The original code here ended up always applying the time zone offset once, and if you had set dhcpv6leaseinlocaltime then it got applied twice, so Sydney at UTC+10:00 would show UTC+20:00 and presumably somewhere at UTC-04:00 would show UTC-08:00

This change makes the code use the same logic as the V4 status_dhcp_leases.php - which works and is simpler.

Note: both the V4 and V6 code format the output, when using local time, as 12-our clock with AM/PM. That seems a bit odd, but I will leave it for now. I will make a separate pull request to change it to 24-hour clock (like is displayed in V4 leases in UTC)
ch1c4um/pfsense,phil-davis/pfsense,dennypage/pfsense,NOYB/pfsense,jxmx/pfsense,phil-davis/pfsense,brunostein/pfsense,ptorsten/pfsense,NOYB/pfsense,NewEraCracker/pfsense,BlackstarGroup/pfsense,pfsense/pfsense,pfsense/pfsense,ch1c4um/pfsense,dennypage/pfsense,dennypage/pfsense,pfsense/pfsense,dennypage/pfsense,NOYB/pfsense,pfsense/pfsense,BlackstarGroup/pfsense,BlackstarGroup/pfsense,ptorsten/pfsense,NewEraCracker/pfsense,NewEraCracker/pfsense,ch1c4um/pfsense,jxmx/pfsense,phil-davis/pfsense,brunostein/pfsense,jxmx/pfsense,phil-davis/pfsense,BlackstarGroup/pfsense,ch1c4um/pfsense,ptorsten/pfsense,brunostein/pfsense,NewEraCracker/pfsense