Comment 2 for bug 1620221

Now that I think of it, looking at the "old" contents of /etc/resolv.conf to see if a line is already there before adding it makes less sense in a resolvconf setting. /etc/resolv.conf is a result combined from various files under /var/run/resolvconf/interface/*. A line in /etc/resolv.conf could come from dhcp6c infor or a different daemon's info.

Perhaps /etc/resolv.conf shouldn't be touched at all if resolvconf isn't running. Might be safe to assume a static config in this case.