Support for Jmx (and Integration) autoconfig in parent contexts

When there are parent contexts we already had a strategy for registering
the actuator endpoints, but not the regular JMX or Integration MBeans.
This chnage makes the autoconfigs for JMX aware of the parent context.

Also adds a sample with a parent context.

See gh-847

spring-boot-samples/spring-boot-sample-integration/src/main/java/sample/integration/ServiceProperties.java

@@ -17,12 +17,16 @@
 package sample.integration;
 
 import org.springframework.boot.context.properties.ConfigurationProperties;
+import org.springframework.jmx.export.annotation.ManagedAttribute;
+import org.springframework.jmx.export.annotation.ManagedResource;
 
 @ConfigurationProperties(prefix = "service", ignoreUnknownFields = false)
+@ManagedResource
 public class ServiceProperties {
 
 	private String greeting = "Hello";
 
+	@ManagedAttribute
 	public String getGreeting() {
 		return this.greeting;
 	}