Fix #3807:
Fix #3807:

* When changing a pre existing VIP, use previous configured interface
  for checking, this fixes the issue that happens when you try to change
  a VIP to a new interface.
* Use the right interface name, only carp uses _vipN suffix

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