This was refactored previously and all the logic should live outside
dhclient-script but it seems it's only loosely handled over there.
For now put a check back in the old way and rework this later correctly
from the system.inc point of view: we do want to register nameserver
and searchdomain in the cache files, but should not add a route if
those are not required. It would be helpful to show them in the overview
regardless (as for DNS servers) but with a hint that they are not being
used.
PR: https://forum.opnsense.org/index.php?topic=26765.0
Moral of the story: don't try to call backend scripts to grab env
variables that you could easily read using the acual nameserver
script sort of like dhclient-script is doing it.
ALLOWOVERRIDE is silly as we guard against that in get_nameservers().
o Only operate the /var/db IP files via rc.newwanip(v6)
o Consistenly flush a cache IP on a triggered reload
o Remove IPv6 address removal workaround from https://redmine.pfsense.org/issues/2627
o Assume that IP is properly checked making $cacheip != $ip a valid assumption when $cacheip is empty
o Remove creation from dhclient script
".ext" came to be because dhclient-script from BSD is also under sbin/,
but since we always explicity use this one just move it to a neutral
location and point to it.
