elastic-agent diagnostics reports an error when contacting endpoint

[michel-laterman]

When running elastic-agent diagnostics status (or just elastic-agent diagnostics) on an agent that is running the endpoint integration, the agent will report a status similar to:

  *  name: endpoint-security  route_key: default
     error: Get "http://unix/": dial unix /opt/Elastic/Agent/data/tmp/default/endpoint-security/endpoint-security.sock: connect: no such file or directory

as endpoint does not use grpc is the same way *beats do.

This should be changed so that the agent reports that endpoint is detected for diagnostics.

[michel-laterman]

This is a bug that effects the current endpoint/agent architecture,
v2 architecture should be able to report metadata as expected (cc @blakerouse)

[cmacknz]

Closing, this is a duplicate of #1965 which was fixed.