java: modify Java example to move healthService to the admin server

[sanjaypujare]

No need to have both health and admin server. So we just add health service to the admin server

CC @ericgribkoff @yashykt @easwars @lidizheng

As per the discussion

[ericgribkoff]

Doesn't our documentation describe creating health checks using the gRPC protocol and the serving port? It looks like moving the health server to a non-serving port would break e.g. https://cloud.google.com/traffic-director/docs/set-up-proxyless-gce#creating_the_health_check_firewall_rule_and_backend_service without an accompanying update to the documentation

[sanjaypujare]

Doesn't our documentation describe creating health checks using the gRPC protocol and the serving port? It looks like moving the health server to a non-serving port would break e.g. https://cloud.google.com/traffic-director/docs/set-up-proxyless-gce#creating_the_health_check_firewall_rule_and_backend_service without an accompanying update to the documentation

Eric, nothing will break. There is also (old code, check https://github.com/GoogleCloudPlatform/traffic-director-grpc-examples/blob/master/java/src/main/java/io/grpc/examples/wallet/StatsServer.java#L179) a health-service on the serving port which is not being removed. The only change is to not create a separate plaintext health-check only port but to overload the admin port to also be the plaintext health check port.

[sanjaypujare]

Friendly ping. Any comments? Can this be approved?

[lidizheng]

The change looks good. I understand that the UHC can't use xDS credentials. Exposing additional health check port sounds good to me.

Please manually trigger https://fusion.corp.google.com/projectanalysis/summary/KOKORO/prod:grpc%2Fwallet-example%2Fmaster%2Fbranch%2Fgrpc_wallet

If possible, please follow the tutorial one more time with this PR https://cloud.google.com/traffic-director/docs/security-proxyless-setup
(Though I don't see breaking changes.)

export EXAMPLES_VERSION=admin-port-mod
export EXAMPLES_REPO=sanjaypujare