services/cluster/vkube: retry build commands
services/cluster/vkube: retry build commands

Retry the build commands up to 3 times to deal with transient errors
especially with gcloud, e.g.

ERROR: gcloud crashed (error): [Errno 111] Connection refused
Change-Id: Iafb2db2cb9acfa6cc93d7b54437b7df30b804cb2

vanadium/go.ref,vanadium/go.ref,vanadium/go.ref,vanadium/go.ref,vanadium/go.ref,vanadium/go.ref