fix(system-upgrade): fix still broken scraping config

This patch should finally resolve the problem for the scraping of the
metrics-server. It seems `kubeadm-flux.conf` was a bad name for the
override as it was loaded *before* the regular `kubeadm.conf` override.

Therefore this patch changes the name to `zz_flux.conf`, which should
**definitely** be loaded afterwards and result in the expected CLI
parameters being used.

infrastructure/system-upgrades/kubelet.yaml

@@ -14,8 +14,8 @@ stringData:
     set -e
     set -x
     secrets="$(dirname $0)"
-    rm -f /etc/systemd/system/kubelet.service.d/flux.conf
-    cp "$secrets/kubelet.service" /etc/systemd/system/kubelet.service.d/kubeadm-flux.conf
+    rm -f /etc/systemd/system/kubelet.service.d/flux.conf /etc/systemd/system/kubelet.service.d/kubeadm-flux.conf
+    cp "$secrets/kubelet.service" /etc/systemd/system/kubelet.service.d/zz_flux.conf
     systemctl daemon-reload
     systemctl restart kubelet.service
 ---