Allow Pulsar Detector to take external endpoint

[addisonj]

Currently, the Pulsar detector simply uses the broker service as it's endpoint.

This means that we aren't validating the proxy (if enabled) or external LBs (if enabled)

I would suggest the following:

• If the user defines an external endpoint (via external dns) or arbitrary endpoint use that
• If the user has a proxy, use that
• otherwise, use broker