SEC-2249: AbstractSecurityWebApplicationInitializer does not delegate WebApplicationInitializer

Previously AbstractSecurityWebApplicationInitializer delegated to a
WebApplicationInitializer, but it caused issues in some instances where
a container would pass the annonymous inner class to
SpringServletContainerInitializer which caused errors on startup.

Now AbstractSecurityWebApplicationInitializer registers the
ContextLoaderListener on its own instead of delegating.