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to handle no sub-second timestamps in mysql

refs CNVS-7032

Change-Id: I86ef91cd6fd6919accf2c2f90bc5482911f66292
Reviewed-on: https://gerrit.instructure.com/28781
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Nick Cloward <ncloward@instructure.com>
QA-Review: Cody Cutrer <cody@instructure.com>
Product-Review: Cody Cutrer <cody@instructure.com>