Improved dashboard documentation with warning on advertised address (#…

…2196)

### Motivation

The dashboard docs should warn user of setting the proper advertised address on standalone service to make it reachable from the stats collector inside Docker.

site/docs/latest/admin/Dashboard.md

@@ -36,7 +36,7 @@ The easiest way to use the dashboard is to run it inside a [Docker](https://www.
 To generate the Docker image:
 
 ```shell
-$ docker build -t pulsar-dashboard dashboard
+$ docker build -t apachepulsar/pulsar-dashboard dashboard
 ```
 
 To run the dashboard:
@@ -52,6 +52,18 @@ You need to specify only one service URL for a Pulsar cluster. Internally, the c
 
 Once the Docker container is running, the web dashboard will be accessible via `localhost` or whichever host is being used by Docker.
 
+{% include admonition.html type="warning" content="The `SERVICE_URL` that the dashboard uses needs to be reachable from inside the Docker container" %}
+
+If the Pulsar service is running in standalone mode in `localhost`, the `SERVICE_URL` would have to
+be the IP of the machine.
+
+Similarly, given the Pulsar standalone advertises itself with localhost by default, we need to
+explicitely set the advertise address to the host IP. For example:
+
+```shell
+$ bin/pulsar standalone --advertised-address 1.2.3.4
+```
+
 ### Known issues
 
 Pulsar [authentication](../../security/overview#authentication-providers) is not supported at this point. The dashboard's data collector does not pass any authentication-related data and will be denied access if the Pulsar broker requires authentication.

site/docs/latest/getting-started/docker.md

@@ -123,7 +123,7 @@ You can find detailed documentation of all the APIs in the [Admin API Overview](
 In the simplest example, you can use curl to probe the stats for a particular topic:
 
 ```shell
-$ curl http://localhost:8080/admin/persistent/public/default/my-topic/stats | python -m json.tool
+$ curl http://localhost:8080/admin/v2/persistent/public/default/my-topic/stats | python -m json.tool
 ```
 
 The output will be something like this: