cordctl: connection error messages are unclear

This message was encountered by a user

cordctl: failed to query for service descriptor "xos.utility": rpc error: code = Unavailable desc = all SubConns are in TransientFailure, latest connection error: timed out waiting for server handshake 

Suspicion is that this was due to the core being unavailable. We need to check and verify if that is the case. It could also be that the core was temporarily unavailable due to service onboarding. Should emit a descriptive error message and a hint for the user to try again.

If this error message is not due to core unavailability, then investigate what did cause it.