consul-template 504 from outside kuberentes cluster and consul in cluster

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for bug reports and enhancements. For general usage questions,
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### Consul Template version

Run `consul-template -v` to show the version. If you are not
running the latest version, please upgrade before submitting an
issue.

consul-template v0.20.0 (b709612c)

### Configuration

```hcl
# Copy-paste your Consul Template configuration file here
consul {
address = "obsfuscated.domain"
auth {
enabled = false
}
retry {
enabled = false
attempts = 12
backoff = "250ms"
}
ssl {
enabled = false
}
}
reload_signal = "SIGHUP"
kill_signal = "SIGINT"
max_stale = "10m"
log_level = "warn"
wait {
min = "5s"
max = "10s"
}
template {
source = "/home/centos/projects/learn-consul-template/test.tpl"
destination = "/home/centos/projects/learn-consul-template/output"
}
```

```liquid
# Copy-paste your Consul Template template here
{{ key "generic/influxdbaddr" }}
```

### Command

```shell
# Place your Consul Template command here
consul-template -config config
```

### Debug output

Provide a link to a GitHub Gist containing the complete debug
output by running with `-log-level=trace`.
```bash
2019/04/30 15:53:58.248009 [ERR] (view) kv.block(generic/influxdbaddr): Unexpected response code: 504 (exceeded maximum retries)
2019/04/30 15:53:58.248042 [ERR] (runner) watcher reported error: kv.block(generic/influxdbaddr): Unexpected response code: 504
2019/04/30 15:53:58.248061 [ERR] (cli) kv.block(generic/influxdbaddr): Unexpected response code: 504
```

### Expected behavior

What should have happened?

I would like consul-template to work (communicating to consul) through kubernetes ingress which is behind aws ELB

### Actual behavior

What actually happened?

504 message consistent with other cases of consul being behind a proxy

### Steps to reproduce

1. run consul-template through kubernetes ingress on aws

### References

Are there any other GitHub issues (open or closed) that should
be linked here? For example:
- GH-1234
- ...

Start with the consul-template v0.20.0 configuration and the trace output showing repeated 504 responses for kv.block through Kubernetes ingress and an AWS ELB. Reproduce the single listed setup, then determine what successful communication with Consul should look like and verify that the template renders without 504 errors.

Written by the indexing model from the issue text.