fixed a defect that was ignoring cancelled participations and thus registrations.  causing duplicate registration objects.
fixed a defect that was ignoring cancelled participations and thus registrations.  causing duplicate registration objects.

also added more restrictions on past participations, checking for sja blocked and blocked status as well.

git-tfs-id: [https://tfs.caes.ucdavis.edu:8088/tfs]$/Commencement/Trunk/Commencement;C9313

ucdavis/Commencement,ucdavis/Commencement,ucdavis/Commencement