Change LinkedIn to be standalone class not mixin.

fixes: CNVS-12498

Test Plan:
* regression test linkedin functionality

Change-Id: I7ba55dea595d6380e68d5a90b272d67807cb55cf
Reviewed-on: https://gerrit.instructure.com/33441
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Simon Williams <simon@instructure.com>
QA-Review: Trevor deHaan <tdehaan@instructure.com>
Product-Review: Jason Madsen <jmadsen@instructure.com>