Azure: Update services that run on control plane nodes

New `update-dns-server` script that adds DNS resolvers to
/etc/NetworkManager/conf.d/dns-servers.conf. The script adds
the host's own IP address and the cloud metadata server's IP
address to the conf file. These would then get added to the
local resolv.conf by NetworkManager.
This script is run as part of azure-update-dns.service
This service runs when the DNSType on the Azure platform
is set to "ClusterHosted".

Author: sadasu

templates/common/azure/units/azure-update-dns.service.yaml

@@ -0,0 +1,19 @@
+name: azure-update-dns.service
+enabled: {{if and (eq .Infra.Status.PlatformStatus.Type "Azure") (.Infra.Status.PlatformStatus.Azure) (.Infra.Status.PlatformStatus.Azure.CloudLoadBalancerConfig) (eq .Infra.Status.PlatformStatus.Azure.CloudLoadBalancerConfig.DNSType "ClusterHosted") }}true{{else}}false{{end}}
+contents: |
+  [Unit]
+  Description=Update Default Azure Resolver
+  # We don't need to do this on the firstboot
+  After=firstboot-osupdate.target
+  # Wait for NetworkManager to report it's online
+  After=NetworkManager-wait-online.service
+  # Run before kubelet
+  Before=kubelet-dependencies.target
+
+  [Service]
+  Type=oneshot
+  RemainAfterExit=yes
+  ExecStart=/usr/local/bin/update-dns-server 169.254.169.254
+
+  [Install]
+  RequiredBy=kubelet-dependencies.target