protected int getProxyPort(String system) {
    return getInt(String.format(CONFIG_PROXY_PORT, system), DEFAULT_CONFIG_PROXY_PORT);
  }
Get the proxy port number as a system level config. This is needed when
users need to go through a proxy for the Kinesis connections.
@param system name of the system
@return proxy port number or 0 if not defined
samza-aws/src/main/java/org/apache/samza/system/kinesis/KinesisConfig.java