Healthcheck support for accessing gremlin in Kubernetes

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**Describe the feature:**
It will be better if we can have a proper health check (returning 200 response) path that can be passed as the readiness probe to the Kubernetes deployments which will lead to backend health check probe creation in managed kubernetes provider like GKE.
**Describe a specific use case for the feature:**
We are looking to expose the janusgraph service to be accessible from an internet exposable HTTPS endpoint with a secure method. With current options in place, we can use a TCP External LB only to expose the service but GKE doesn't support SSL proxy LB to it.
Ingress looks like a feasible solution but the health check creation fails due to the lack of 200 response on default /healthz path . I can see a health check file in tmp directory which executes a python file to get the response. Not sure if we can use that to fix this.
Ref link1: https://github.com/helm/charts/blob/master/stable/janusgraph/values.yaml
Ref link2: https://github.com/FairwindsOps/helm-charts/blob/master/stable/janusgraph/templates/deployment.yaml#L37
python file content:
```
import json, urllib2

response = json.loads(urllib2.urlopen('http://localhost:8182?gremlin=graph.open').read())["result"]["data"][0]
print (response)
assert response == True
```
Which returns 'True' in response.

Start by reviewing the Kubernetes deployment and health-check configuration in the referenced Helm chart files, then inspect how the existing Python check calls the Gremlin endpoint at localhost:8182. Define and verify a health-check path that returns HTTP 200 for the readiness probe and supports the stated GKE ingress use case.

Written by the indexing model from the issue text.