Unregister class with invalid __module__ after test is done.

Components are saved to ComponentMeta._components class variable (shared
between all tests run in the same process). When get_plugin_info is called,
it traverses this list of registered classes, and fails if a class with
invalid __module__ is encountered. 


git-svn-id: https://svn.apache.org/repos/asf/bloodhound/trunk@1486658 13f79535-47bb-0310-9956-ffa450edef68