When management endpoints are on a different port the HandlerMappings
are restricted to a single EndpointHandlerMapping, so the error
controller (which is a normal @Controller with @RequestMappings) does
not get mapped.
Fixed by addinga shim Endpoint on "/error" that delegates to the
ErrorController (which interface picks up an extra method).
The management endpoints were still all mixed up
with the user endpoints. Fixed that and extracted
user endpoints in to conditional block so not
protected if path explicitly set to empty string.
[#53029715]
