Bump flatcar image

The previous one was deleted by mistake, use a newer one that is
available.

Author: mandre

hack/ci/cloud-init/controller.yaml.tpl

@@ -83,7 +83,7 @@
     IMAGE_URLS+="https://storage.googleapis.com/artifacts.k8s-staging-capi-openstack.appspot.com/test/cirros/2022-12-05/cirros-0.6.1-x86_64-disk.img,"
     IMAGE_URLS+="https://storage.googleapis.com/artifacts.k8s-staging-capi-openstack.appspot.com/test/ubuntu/2023-09-29/ubuntu-2204-kube-v1.27.2.img,"
     IMAGE_URLS+="https://storage.googleapis.com/artifacts.k8s-staging-capi-openstack.appspot.com/test/ubuntu/2023-09-29/ubuntu-2204-kube-v1.28.2.img,"
-    IMAGE_URLS+="https://storage.googleapis.com/artifacts.k8s-staging-capi-openstack.appspot.com/test/flatcar/flatcar-stable-3602.2.0-kube-v1.28.2.img"
+    IMAGE_URLS+="https://storage.googleapis.com/artifacts.k8s-staging-capi-openstack.appspot.com/test/flatcar/flatcar-stable-3815.2.0-kube-v1.28.5.img"
 
     [[post-config|$NOVA_CONF]]
     [DEFAULT]

test/e2e/data/e2e_conf.yaml

@@ -197,7 +197,7 @@ variables:
   # The default user for SSH connections from bastion to machines
   SSH_USER_MACHINE: "ubuntu"
   EXP_KUBEADM_BOOTSTRAP_FORMAT_IGNITION: "true"
-  OPENSTACK_FLATCAR_IMAGE_NAME: "flatcar-stable-3602.2.0-kube-v1.28.2"
+  OPENSTACK_FLATCAR_IMAGE_NAME: "flatcar-stable-3815.2.0-kube-v1.28.5"
 
 intervals:
   conformance/wait-control-plane: ["30m", "10s"]