I'm trying to roll out a fresh Kubernetes cluster on nodes running Kubic (using
systemd-networkd, if that could be related).

Shortly after running `kubeadm init` and `KUBECONFIG=/etc/kubernetes/admin.conf
kubectl apply -f /usr/share/k8s-yaml/weave/weave.yaml` to add the CNI, then
pasting the join command into other nodes, I'm seeing pods fail to start with
events like this (on a coredns pod):


```
  Warning  FailedCreatePodSandBox  5m49s                  kubelet           
Failed to create pod sandbox: rpc error: code = Unknown desc = failed to create
pod network sandbox
k8s_coredns-758b886957-ps5wc_kube-system_ddf332ce-dc22-4a03-8e4a-d5ee904936be_0(1a3938c9b41b9f0186a8e156b11b608bf606a7ed510df158921c09009063263e):
error adding pod kube-system_coredns-758b886957-ps5wc to CNI network "weave":
unable to allocate IP address: Post
"http://127.0.0.1:6784/ip/1a3938c9b41b9f0186a8e156b11b608bf606a7ed510df158921c09009063263e":
dial tcp 127.0.0.1:6784: connect: connection refused
  Warning  FailedCreatePodSandBox  5m35s                  kubelet           
Failed to create pod sandbox: rpc error: code = Unknown desc = failed to create
pod network sandbox
k8s_coredns-758b886957-ps5wc_kube-system_ddf332ce-dc22-4a03-8e4a-d5ee904936be_0(ee4eb51fb8e49730c1d40d28af0116e2b34f9ad7d38abc67bcd91d112a20d7f9):
error adding pod kube-system_coredns-758b886957-ps5wc to CNI network "weave":
unable to set hairpin mode to true for bridge side of veth vethweplee4eb51:
operation not supported
  Warning  FailedCreatePodSandBox  5m20s                  kubelet           
Failed to create pod sandbox: rpc error: code = Unknown desc = failed to create
pod network sandbox
k8s_coredns-758b886957-ps5wc_kube-system_ddf332ce-dc22-4a03-8e4a-d5ee904936be_0(6eea0c1bf1cb6cc9a6cd10901f34acbe2db16995105322dd03f35d2062e62c8f):
error adding pod kube-system_coredns-758b886957-ps5wc to CNI network "weave":
unable to set hairpin mode to true for bridge side of veth vethwepl6eea0c1:
operation not supported
  Warning  FailedCreatePodSandBox  5m7s                   kubelet           
Failed to create pod sandbox: rpc error: code = Unknown desc = failed to create
pod network sandbox
k8s_coredns-758b886957-ps5wc_kube-system_ddf332ce-dc22-4a03-8e4a-d5ee904936be_0(0a6110d500f0dffc97244f1836a2a99240e401c6fe8331d4df13ee43349fafb6):
error adding pod kube-system_coredns-758b886957-ps5wc to CNI network "weave":
unable to set hairpin mode to true for bridge side of veth vethwepl0a6110d:
operation not supported
```

This happens for other pods I add to the cluster, too (for example, when
installing Flux 2): they all get stuck with errors like this.