502 Bad gateway: Hazelcast Management Center via GCE Ingress

For those of you who will be exposing Hazelcast Management Center (MC) via Google's Ingress GCE controller - be aware that GCE Ingress is expecting a working (should be ``200 OK``) readiness probe from the Service backing the MC Deployment.

I tried with the defaults and got ``502 Bad gateway`` when accessing the exposed MC service. You can read about similar experience [here](https://github.com/kubernetes/ingress-gce/issues/317).

Note also, that the default endpoint ``/hazelcast-mancenter`` returns ``302 Found``, which is ok for the readiness probe, but apparently not for GCE Ingress. The quick hack would be to use either ``/hazelcast-mancenter/index.html`` or ``/hazelcast-mancenter/``. But in the long term I would propose to implement a dedicated health probe, e.g. ``/health`` or ``/healthz``, etc.

So ``302 Found`` is ok for checking the readiness of the Service, but if you check the status of the ingress, you will probably see the ``UNHEALTHY`` status:
```
k describe ing mc-ingress
Name: mc-ingress
Namespace: default
Address: 34.98.YYY.2
Default backend: mc-service:8080 (10.52.2.23:8080)
Rules:
Host Path Backends
---- ---- --------
* * mc-service:8080 (10.52.2.23:8080)
Annotations:
ingress.kubernetes.io/backends: {"k8s-be-32517--47d3253409234a5d":"UNHEALTHY"}
Events:
```

Here is a working yaml:
```
apiVersion: v1
kind: PersistentVolumeClaim
metadata:
name: mc-volume
spec:
accessModes:
- ReadWriteOnce
resources:
requests:
storage: 1Gi
---
apiVersion: apps/v1
kind: Deployment
metadata:
name: mc
labels:
app: hazelcast
spec:
replicas: 1
selector:
matchLabels:
app: hazelcast
template:
metadata:
labels:
app: hazelcast
spec:
containers:
- name: mc
image: hazelcast/management-center
resources:
limits:
memory: 1Gi
ports:
- containerPort: 8080
livenessProbe:
httpGet:
path: /hazelcast-mancenter/
port: 8080
readinessProbe:
httpGet:
path: /hazelcast-mancenter/
port: 8080
volumeMounts:
- name: mc-storage
mountPath: /data
volumes:
- name: mc-storage
persistentVolumeClaim:
claimName: mc-volume
---
apiVersion: v1
kind: Service
metadata:
name: mc-service
spec:
type: NodePort
selector:
app: hazelcast
ports:
- protocol: TCP
port: 8080
targetPort: 8080
---
apiVersion: extensions/v1beta1
kind: Ingress
metadata:
name: mc-ingress
labels:
app: hazelcast
spec:
backend:
serviceName: mc-service
servicePort: 8080
```

P.S. Nginx Ingress doesn't have such issue. But a dedicated health endpoint is a nice to have non the less.