spec: fix sporadic media comment spec failures

delayed jobs from a previous (non-transactional) spec were causing the
expectations to fail

Change-Id: I0b4c2db3e4b2baa0a3416233c18e5ec3230cdfb2
Reviewed-on: https://gerrit.instructure.com/38607
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Bryan Madsen <bryan@instructure.com>
Product-Review: Bryan Madsen <bryan@instructure.com>
QA-Review: Bryan Madsen <bryan@instructure.com>