CQS: selenium spec for canvas integration

Added a selenium spec that visits the statistics_cqs page and verifies
that the client app has loaded and mounted successfully.

Closes CNVS-15363

Change-Id: I4a87b5af78343d51ef8e4c0b1e30065eff9e7d6b
Reviewed-on: https://gerrit.instructure.com/40775
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Derek DeVries <ddevries@instructure.com>
QA-Review: Derek DeVries <ddevries@instructure.com>
Product-Review: Ahmad Amireh <ahmad@instructure.com>