private void putInInstanceCache(String key, Map<String, InstanceType> cache,
      InstanceType instance) {
    cache.put(key, instance);
  }
Get the ensemble server addresses from the configuration. The format is: host1:port,
host2:port..

@param conf configuration
llap-client/src/java/org/apache/hadoop/hive/registry/impl/ZkRegistryBase.java