fix callback suspension for ruby 2

need to check for private methods

Change-Id: I5b51b3da9ab3baa8b619c10b684d96fe685a0c9d
Reviewed-on: https://gerrit.instructure.com/36749
Reviewed-by: Jacob Fugal <jacob@instructure.com>
Tested-by: Jenkins <jenkins@instructure.com>
Product-Review: Cody Cutrer <cody@instructure.com>
QA-Review: Cody Cutrer <cody@instructure.com>