fix(coreos-base/oem-vagrant): Use generic cloud config unit.

sdk_container/src/third_party/coreos-overlay/coreos-base/oem-vagrant/files/cloud-config.yml

@@ -7,20 +7,7 @@ coreos:
         content: |
           [Path]
           PathExists=/var/lib/coreos-vagrant/user-data
-
-          [Install]
-          WantedBy=multi-user.target
-      - name: coreos-cloudinit-vagrant.service
-        runtime: no
-        content: |
-          [Unit]
-          ConditionFileNotEmpty=/var/lib/coreos-vagrant/user-data
-
-          [Service]
-          Type=oneshot
-          EnvironmentFile=-/etc/environment
-          ExecStart=/usr/bin/coreos-cloudinit --from-file /var/lib/coreos-vagrant/user-data
-          RemainAfterExit=yes
+          Unit=user-cloudinit@var-lib-coreos\x2dvagrant-user\x2ddata.service
     oem:
       id: vagrant
       name: Vagrant