Allow for es scheme (https, http) to be configurable via container's env var

[markmark206]

What changed?

This is a change for #562. With this change, temporal container can be configuring to use a scheme other than http (such as https;) to connect to elastic search.

This change goes along with temporalio/helm-charts#49

Why?
A customer reported that this is the behavior they would expect, but that was not the actual behavior.

How did you test it?

I built the docker image and deployed it to a k8s cluster, using temporal helm chart (temporalio/helm-charts#49), passing in "ES_SCHEME: https" env var. I made sure the env var took effect (I didn't have an ES listening on HTTPS port so the connection failed to esablish, as expected).

◉ 22:44:48 [markmark ~/src/temporal-helm-charts] (master|m1u) $ helm install temporaltest --set elasticsearch.scheme=https --set server.kafka.host=kafkat-headless:9092 --set grafana.enabled=false --set kafka.enabled=false --set prometheus.enabled=false -f values/values.cassandra.yaml -f values/values.elasticsearch.yaml --set server.image.tag=markmark-local2 --set server.image.repository=markmark206/server --set admintools.image.tag=bfa0fce6ca193a6cd987402341e126f391764ec9 --set admintools.image.repository=markmark206/admin-tools . --timeout 15m --wait
...
operation timed out

I also tested with "ES_SCHEME: https" and made sure things continue to work.

◉ 22:42:52 [markmark ~/src/temporal-helm-charts] (master|m1u) $ helm install temporaltest --set server.kafka.host=kafkat-headless:9092 --set grafana.enabled=false --set kafka.enabled=false --set prometheus.enabled=false -f values/values.cassandra.yaml -f values/values.elasticsearch.yaml --set server.image.tag=markmark-local2 --set server.image.repository=markmark206/server --set admintools.image.tag=bfa0fce6ca193a6cd987402341e126f391764ec9 --set admintools.image.repository=markmark206/admin-tools . --timeout 15m --wait
NAME: temporaltest
LAST DEPLOYED: Fri Jul 17 22:44:01 2020
NAMESPACE: default
STATUS: deployed
REVISION: 1
NOTES:
To verify that Temporal has started, run:

  kubectl --namespace=default get pods -l "app.kubernetes.io/instance=temporaltest"

Potential risks

Elastic search connectivity might become broken.