Work around silly limitation of 6 search domains in /etc/resolv.conf.

Work around silly limitation of 6 search domains in /etc/resolv.conf.
This limitation was removed from the GNU C library release 2.26 in 2017
but Kubernetes still enforces it. Kubernetes uses 3 search domains. This
is no problem on Minikube, but on GKE the other 3 slots are populated by
GCP.

We can actually edit resolv.conf, but only in place, which is why we
fall back on `ed`...

No issue #

Arvados-DCO-1.1-Signed-off-by: Ward Vandewege <ward@jhvc.com>