spec: fix brittle spec

this one fails more than it passes, due to test code running before
handlers are added asynchronously

Change-Id: I4f5c8ffeadb3a50ba580e9bd221135bd433bfc23
Reviewed-on: https://gerrit.instructure.com/44500
Tested-by: Jenkins <jenkins@instructure.com>
Product-Review: Michael Ziwisky <mziwisky@instructure.com>
Reviewed-by: Michael Ziwisky <mziwisky@instructure.com>
QA-Review: Michael Ziwisky <mziwisky@instructure.com>