Nuke interface_track6_dhcp6_configure()
Nuke interface_track6_dhcp6_configure()

This function does 2 unecessary things:

. Remove the IP address from interface set as Track, what is wrong and
  should be done by dhcp6c
. Set a fixed IP when track6-interface is SLAAC, what never happens
  since it's impossible to track a SLAAC interface

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