make a text link into a actual hyperlink

the text link doesn't fit on some screen resolutions. Making it into sphinx hyperlink will solve that

cloud/docker/docker.py

@@ -111,8 +111,8 @@ options:
     version_added: "2.0"
   log_opt:
     description:
-      - Additional options to pass to the logging driver selected above. See Docker log-driver
+      - Additional options to pass to the logging driver selected above. See Docker `log-driver 
-        documentation for more information (https://docs.docker.com/reference/logging/overview/).
+        <https://docs.docker.com/reference/logging/overview/>` documentation for more information.
         Requires docker >=1.7.0.
     required: false
     default: null