SAK-23733 - Fix up circular bean references

Because of the complexity involved in tracking external items, the
GradebookExternalAssessmentService needs access to the GradebookService.
Injecting the bean directly can cause Spring loading errors, so this
change uses the ComponentManager to retrieve the service on demand.

This co-dependency is less than ideal, but resolving it would be more
involved and probably require unacceptable API changes.

Thanks to Kevin T for the patch.



git-svn-id: https://source.sakaiproject.org/svn/edu-services/trunk@126997 66ffb92e-73f9-0310-93c1-f5514f145a0a