Support connect sidecar without a network port

#### Feature Description

Please support Connect sidecar proxy that does not require the service to expose a network port. Right now Connect registers a healthcheck in consul that will fail if the service is not reachable by the sidecar, this causes problems for a service that only exists for background tasks and does not offer functionality over the network.

#### Use Case(s)

Background workers, cron and services with similar nature where it is still necessary for the service to communicate with other connect enabled services but it does not expect inbound network connection.