Fix issue with etcd-member failing to resolve peers

* When restarting masters, `etcd-member.service` may fail to lookup peers if
/etc/resolv.conf hasn't been populated yet. Require the wait-for-dns.service.

aws/container-linux/kubernetes/cl/controller.yaml.tmpl

@@ -41,6 +41,7 @@ systemd:
         ExecStart=/bin/sh -c 'while ! /usr/bin/grep '^[^#[:space:]]' /etc/resolv.conf > /dev/null; do sleep 1; done'
         [Install]
         RequiredBy=kubelet.service
+        RequiredBy=etcd-member.service
     - name: kubelet.service
       enable: true
       contents: |

bare-metal/container-linux/kubernetes/cl/controller.yaml.tmpl

@@ -50,6 +50,7 @@ systemd:
         ExecStart=/bin/sh -c 'while ! /usr/bin/grep '^[^#[:space:]]' /etc/resolv.conf > /dev/null; do sleep 1; done'
         [Install]
         RequiredBy=kubelet.service
+        RequiredBy=etcd-member.service
     - name: kubelet.service
       contents: |
         [Unit]

digital-ocean/container-linux/kubernetes/cl/controller.yaml.tmpl

@@ -50,6 +50,7 @@ systemd:
         ExecStart=/bin/sh -c 'while ! /usr/bin/grep '^[^#[:space:]]' /etc/resolv.conf > /dev/null; do sleep 1; done'
         [Install]
         RequiredBy=kubelet.service
+        RequiredBy=etcd-member.service
     - name: kubelet.service
       contents: |
         [Unit]

google-cloud/container-linux/kubernetes/controllers/cl/controller.yaml.tmpl

@@ -41,6 +41,7 @@ systemd:
         ExecStart=/bin/sh -c 'while ! /usr/bin/grep '^[^#[:space:]]' /etc/resolv.conf > /dev/null; do sleep 1; done'
         [Install]
         RequiredBy=kubelet.service
+        RequiredBy=etcd-member.service
     - name: kubelet.service
       enable: true
       contents: |