KAFKAREST_OPTS is not being used while ensuring that kafka cluster is up and ready

[infoankitp]

So, basically if we are passing the KAFKAREST_OPTS as suggested here:
https://docs.confluent.io/platform/current/kafka-rest/production-deployment/rest-proxy/security.html#authentication-between-crest-and-ak-brokers

While the ensure bash file runs, this env variable is not taken into account and kafka cluster validation fails even before starting the application server for kafka rest proxy.

https://github.com/confluentinc/confluent-docker-utils/blob/master/confluent/docker_utils/cub.py#L149-L205

One quick way of solving it can be to pick up other values in check_kafka_ready() function, but it seems I am not sure about its usage at multiple other places. However, kafka-rest's deployment fails on only passing the KAFKAREST_OPTS. We have to add one more env variable KAFKA_OPTS for the same as a workaround.