make migration non transactional

refs: CNVS-11546

Test Case: Migration should work.

Change-Id: Ic3a2c18ef4e4f25327a49ba98ecc3e810d6186cb
Reviewed-on: https://gerrit.instructure.com/34140
Reviewed-by: Cody Cutrer <cody@instructure.com>
QA-Review: August Thornton <august@instructure.com>
Product-Review: Cody Cutrer <cody@instructure.com>
Tested-by: Brian Palmer <brianp@instructure.com>