Node e2e test runner - run against images

- support allocating gce instances from images and running tests against them
- set --hostname-override to match node name
- add jenkins script to source to reproduce jenkins build locally

hack/verify-flags/known-flags.txt

@@ -151,6 +151,7 @@ input-dirs
 insecure-bind-address
 insecure-port
 insecure-skip-tls-verify
+instance-name-prefix
 iptables-masquerade-bit
 iptables-sync-period
 ir-data-source