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/pom.xml

@@ -39,6 +39,7 @@
 		<module>spring-boot-sample-integration</module>
 		<module>spring-boot-sample-jetty</module>
 		<module>spring-boot-sample-liquibase</module>
+		<module>spring-boot-sample-parent-context</module>
 		<module>spring-boot-sample-profile</module>
 		<module>spring-boot-sample-secure</module>
 		<module>spring-boot-sample-servlet</module>