Datadog Integration Not Viable for Terminating Gateways

#### Overview of the Issue

We have a large consul deployment, we have a few terminating gateways for things like lambda services etc. What we've noticed is that it seems with the datadog integration for consul, metrics like:

consul.catalog.nodes_up and the like, terminating gateways don't show up at all, even though they're technically a service.

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#### Reproduction Steps

Run a terminating gateway, consul version 1.13.X+ (we've seen this from 1.10.X)
Run a datadog agent with it

No consul statistics will flow, (envoy statistics do, but the tags are out of order)