Fix management endpoint without Spring Security

The method 'injectIntoSecurityFilter' added In 3c1e48c assumes that
Spring security is in the classpath so any management endpoints that are
deployed on a different port requires Spring Security all the sudden.

This commit separates the creating of the EndpointHandlerMapping in two
mutually exclusive @Configuration: one that is triggered if Spring
Security is not in the classpath and one that is triggered if Spring
Security is in the classpath. The latter apply the security filter in the
endpoint mapping if it exists.

Fixes gh-2124