Previously, #containsBean Javadoc advertised that a true return value
indicates that a call to #getBean for the same name would succeed.
This is actually not the case, and has never been. The semantics
of #containsBean have always been to indicate whether a bean definition
with the given name is definied or a singleton instance with the given
name has been registered.
The Javadoc now reflects this accurately.
Issue: SPR-8690