ClassNotFoundException in SpringHawtioContextListener

[creckord]

After upgrading from HawtIO 2.14.5 to 2.15.0, our applications won't start anymore due to a ClassNotFoundException in SpringHawtioContextListener:

java.lang.ClassNotFoundException: ch.qos.logback.core.Appender
	at jdk.internal.loader.BuiltinClassLoader.loadClass(Unknown Source) ~[?:?]
	at jdk.internal.loader.ClassLoaders$AppClassLoader.loadClass(Unknown Source) ~[?:?]
	at java.lang.ClassLoader.loadClass(Unknown Source) ~[?:?]
	at io.hawt.springboot.SpringHawtioContextListener.<init>(SpringHawtioContextListener.java:21) ~[hawtio-springboot-2.15.0.jar:2.15.0]	
	at io.hawt.springboot.HawtioManagementConfiguration.hawtioContextListener(HawtioManagementConfiguration.java:279) ~[hawtio-springboot-2.15.0.jar:2.15.0]

This is caused by the following addition in PR 2732:

+               this.logQuery = new LogbackLogQuery();

We are using Log4J2 in our aplications, and Logback is not part of the deployment.

Since SpringHawtioContextListener is part of hawtio-springboot and not of the hawtio-log-logback plugin, I don't think it should have a hard requirement on Logback. And since the bean configuration in HawtioManagementConfiguration is unconditional, it's also hard to override with a different implementation.