CLC-4132 - Fix bug with instructor enrollments when section has leading zero

https://jira.ets.berkeley.edu/jira/browse/CLC-4132

Working fix. Rspec for Canvas::SiteMembershipsMaintainer randomly fails. This seems to be due to random test data setup, but requires further investigation.
CampusOracle::Queries.get_section_instructors receives CCN in non-zero-padded format. I found this to be necessary due to the nature of the test.