Try to reduce flakiness in install_k8s_on_robot.sh
Try to reduce flakiness in install_k8s_on_robot.sh

From analyzing CI logs, most of the layer-0 test's flakes appear to be
failures when running apt-get update. Once kubeadm failed to pull the
control plane images.

Adding retries to these steps reduces the flakiness from ~30% to ~3%
flakes.

The remaining flakes appear to occur when `apt-get update` succeeds but
leaves the indices in a bad state, so `apt-get install` fails. Since
it's not clear how to detect/resolve that automatically, I've adjusted
the error message to suggest updating before installing.

b/126867575

Change-Id: I4326dd0ad2e7a3995d794fb0cca47f437c95220c
GitOrigin-RevId: b4d16dda7f8f4557291d68183da8dd401366d552

googlecloudrobotics/core,googlecloudrobotics/core,googlecloudrobotics/core