@Override
					public void onApplicationEvent(ApplicationEnvironmentPreparedEvent event) {
						event.getEnvironment().getPropertySources().addFirst(
								new PropertiesPropertySource("executorEnvironment", properties));
					}
This method called by {@link MessageBusReceiver} and {@link MessageBusSender} to setup
message bus configuration at the spark module executor process. This configuration
should use the same properties configured in XD container that deployed the spark
streaming module.

@param properties the message bus properties
@return the application context that has MessageBus bean
spring-xd-dirt/src/main/java/org/springframework/xd/dirt/plugins/spark/streaming/MessageBusConfiguration.java