ci: Force minikube to use localkube

The default is `kubeadm`, which requires systemd, which is not present
on Trusty, which is what's used by both CircleCI and Travis.

This change should be reverted once this issue is fixed: kubernetes/minikube#2704

.circleci/config.yml

@@ -16,7 +16,8 @@ jobs:
             curl -Lo kubectl https://storage.googleapis.com/kubernetes-release/release/${K8S_VERSION}/bin/linux/amd64/kubectl && chmod +x kubectl && sudo mv kubectl /usr/local/bin/
             curl -Lo minikube https://github.com/kubernetes/minikube/releases/download/${MINIKUBE_VERSION}/minikube-linux-amd64 && chmod +x minikube && sudo mv minikube /usr/local/bin/
             sudo minikube config set WantReportErrorPrompt false
-            sudo -E minikube start --vm-driver=none --kubernetes-version=${K8S_VERSION} --extra-config=apiserver.Authorization.Mode=RBAC
+            # TODO: remove the --bootstrapper flag once this issue is solved: https://github.com/kubernetes/minikube/issues/2704
+            sudo -E minikube start --vm-driver=none --bootstrapper=localkube --kubernetes-version=${K8S_VERSION} --extra-config=apiserver.Authorization.Mode=RBAC
       - run:
           name: code-gen script
           environment:

.travis.yml

@@ -27,7 +27,8 @@ before_script:
 # Download minikube.
 - curl -Lo minikube https://github.com/kubernetes/minikube/releases/download/${MINIKUBE_VERSION}/minikube-linux-amd64 && chmod +x minikube && sudo mv minikube /usr/local/bin/
 - sudo minikube config set WantReportErrorPrompt false
-- sudo minikube start --vm-driver=none --kubernetes-version=${K8S_VERSION} --extra-config=apiserver.Authorization.Mode=RBAC
+# TODO: remove the --bootstrapper flag once this issue is solved: https://github.com/kubernetes/minikube/issues/2704
+- sudo minikube start --vm-driver=none --bootstrapper=localkube --kubernetes-version=${K8S_VERSION} --extra-config=apiserver.Authorization.Mode=RBAC
 # Fix the kubectl context, as it's often stale.
 - minikube update-context
 # Clone the code generator repo