Check if ReflectionMethod::getDocComment is working

Some caches/accelerators has settings to strip comments. This makes AppFrameworks MethodAnnotationReader fail and thus rendering apps built using AppFramework inaccessible.

https://github.com/owncloud/core/issues/6840#issuecomment-36902355 and the following comments.

@DeepDiver1975 @karlitschek @Raydiation