kubernetes: allow pre-pulling the multiversion image on k8s nodes
Allow pulling the multiversion image on all k8s nodes before doing any deployment beyond the testserver.
This is done to ensure that all nodes will have the image available when deployments happen, reducing on average the worst pull time from 6-7 minutes to a few seconds.
Bug: T323349 Change-Id: Ib15e04dff43e4ef52bcd6025ac6747cde3b49dae