Use ucp_latest_image and update docker_image page variables (#2746)

* Bump UCP patch version to 2.1.3

* Use ucp_latest_image and update docker_image page variables

_config.yml

@@ -128,7 +128,7 @@ defaults:
     values:
       ucp_version: "2.1"
       dtr_version: "2.2"
-      docker_image: "docker/ucp:2.1.2"
+      docker_image: "docker/ucp:2.1.3"
   -
     scope:
       path: "datacenter/ucp/2.0"

datacenter/ucp/2.1/guides/admin/install/index.md

@@ -61,12 +61,12 @@ To install UCP:
 
     ```none
     # Pull the latest version of UCP
-    $ docker pull {{ page.docker_image }}
+    $ docker pull {{ page.ucp_latest_image }}
 
     # Install UCP
     $ docker run --rm -it --name ucp \
       -v /var/run/docker.sock:/var/run/docker.sock \
-      {{ page.docker_image }} install \
+      {{ page.ucp_latest_image }} install \
       --host-address <node-ip-address> \
       --interactive
     ```