fix migrations that don't send later, even if prod

(i.e. new shards)

Change-Id: I2c66bcdc087229eb827cb4b91a2734723fdefbe9
Reviewed-on: https://gerrit.instructure.com/40578
Reviewed-by: Brian Palmer <brianp@instructure.com>
Tested-by: Jenkins <jenkins@instructure.com>
Product-Review: Cody Cutrer <cody@instructure.com>
QA-Review: Cody Cutrer <cody@instructure.com>