Fix #432: Change db service to headless needed to get direct pod dns name on GKE

[guymguym]

Explain the changes

1. Without this on GKE we don't get the DNS name of the pod created noobaa-db-pg-0.noobaa-db-pg.<namespace>.svc
2. see https://kubernetes.io/docs/concepts/services-networking/dns-pod-service/#pod-s-hostname-and-subdomain-fields
3. see https://kubernetes.io/docs/concepts/services-networking/service/#headless-services
4. For some reason on Openshift this works also for non-headless service, but on GKE it won't generate the DNS for the pods unless it's headless (see with kubectl get endpointslices).

Issues: Fixed #xxx / Gap #xxx

1. Fixes [BUG] NooBaa is not working in GKE #432

Testing Instructions:

1. Deploy on GKE

[roveicy93]

Hi @guymguym , please let me know when we can test this fix. Thank you for your kind support.