user merge guard spec when enrolled in same course
user merge guard spec when enrolled in same course

refs FOO-2948
flag = none

Test plan:
 • guard spec

Change-Id: Id117fad52bf0cf73777bbbd9291cbfb7b819bd78
Reviewed-on: https://gerrit.instructure.com/c/canvas-lms/+/293256
Tested-by: Service Cloud Jenkins <9144042a601061f88f1e1d7a1753ea3e2972119d@instructure.com>
Reviewed-by: Sean Scally <ceb34b930afeb707ad0575cfce0e31dce3c15014@instructure.com>
Reviewed-by: Charley Kline <05950d7e90ba5e3da323378368c22b3ffaaf6647@instructure.com>
QA-Review: August Thornton <9adc7a1161ddf32ff608de792a7e50179545f026@instructure.com>
Product-Review: August Thornton <9adc7a1161ddf32ff608de792a7e50179545f026@instructure.com>

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