Custom application with empty `getClasses()/getSingletons()` registering also NON root resources

[frantuma]

It seems that Jersey (at least 2.26) incorrectly registers also non root resources (available via getClasses()) even if stated otherwise in docs section 4.7.2.3.2. JAX-RS application with a custom Application subclass

#1867 and #1906 addressed different issues in this area

An example of this behaviour can be found here