show Quizzes.Next button on course homepage
show Quizzes.Next button on course homepage

the Assignments page's header shows Quizzes.Next button if the LTI
is active. Course homepage controller now does same check

fixes ADMIN-1074

test plan:
 - Enable Quizzes.Next feature flag and install LTI
 - Ensure Assignments page shows Quizzes.Next button as expected
 - Set Assignments as Course homepage
 - verify course homepage shows Quizzes.Next button

Change-Id: I40ebe01766538c1ed074cbd8a69c70c8951e6f16
Reviewed-on: https://gerrit.instructure.com/153361
Tested-by: Jenkins
Reviewed-by: Jeremy Stanley <b3f594e10a9edcf5413cf1190121d45078c62290@instructure.com>
QA-Review: Ed Schiebel <0ca8a83847a5889cf05cb219c0ab09f6b646243b@instructure.com>
Product-Review: Carl Kibler <7c2b40129dd885a147d5b2dda56dda016b9a8f57@instructure.com>

instructure/canvas-lms,instructure/canvas-lms,djbender/canvas-lms,sfu/canvas-lms,djbender/canvas-lms,sfu/canvas-lms,sfu/canvas-lms,instructure/canvas-lms,instructure/canvas-lms,sfu/canvas-lms,sfu/canvas-lms,sfu/canvas-lms,djbender/canvas-lms,instructure/canvas-lms,djbender/canvas-lms,sfu/canvas-lms,instructure/canvas-lms,instructure/canvas-lms