AprLifecycleListener is configured even though Tomcat's native library is not available

[wilkinsona]

When an app using Tomcat starts up, due to the presence of the AprLifecycleListener, it logs the following info message:

2019-02-26 13:59:29.961  INFO 67175 --- [           main] o.a.catalina.core.AprLifecycleListener   : The APR based Apache Tomcat Native library which allows optimal performance in production environments was not found on the java.library.path: …

I think, and it's only an educated guess, that this is causing some confusion and leading people to believe that Tomcat isn't going to perform well in production. The listener was added in 5f57578. I wonder if there's a way to be a bit smarter about when we add it and only add it when it will be used.

[wilkinsona]

I think we could create an instance, call AprLifecycleListener.isAvailable() (it's a static method but creating the instance has a side-effect that affects the result of isAvailable()) and then only add the listener if the result is true.