Update LinksMvcEndpoint and HalBrowserMvcEndpoint so that no longer try
to use the `/` context path. Links are now available from `/links` and
the HAL browser is available from `/hal`.
The actuator HAL browser now works with either WebJars or the Spring
Data version. It also now transforms the initial HTML so that the
form is pre-populated with `/links`.
When using Spring Data's HAL browser, the root includes a link to
`/links` with a rel of `actuator`.
See gh-3621
When Spring Data REST is owning the home page it has its own
HandlerMapping with a fix (relatively) low priority. The /links
endpoint wants to own the home page as well, and our handler mapping
has a high priority for good reasons. This change addresses the
issue by checking if Spring Data REST is configured and if
the management context path (or more specifically, the links
endpoint) is the same as the home page.
Fixes gh-3486
