Make kubeadm job friendlier for local execution.

This lets users gracefully invoke the job's Docker image with mounted
volumes for the necessary repositories (instead of cloning them).
Previously, they would have to comment out these "git clone" lines and
rebuild the image or encounter an error because the directories already
existed.

images/ci-kubernetes-e2e-kubeadm/runner

@@ -17,12 +17,19 @@ set -o errexit
 set -o nounset
 set -o pipefail
 
-git clone https://github.com/kubernetes/test-infra
-git clone https://github.com/kubernetes/kubernetes-anywhere
+if [ ! -e test-infra ]; then
+  git clone https://github.com/kubernetes/test-infra
+fi
+
+if [ ! -e kubernetes-anywhere ]; then
+  git clone https://github.com/kubernetes/kubernetes-anywhere
+fi
 
 # This is required until https://github.com/kubernetes/kubernetes-anywhere/issues/332
 # is implemented.
-ln -s "${GOOGLE_APPLICATION_CREDENTIALS}" kubernetes-anywhere/phase1/gce/account.json
+if [ ! -e kubernetes-anywhere/phase1/gce/account.json ]; then
+  ln -s "${GOOGLE_APPLICATION_CREDENTIALS}" kubernetes-anywhere/phase1/gce/account.json
+fi
 
 ./test-infra/jenkins/bootstrap.py \
     --repo="k8s.io/${REPO_NAME}" \