Fix mflag test issue with "ResetForTesting" (which only showed up under dyntest for some odd reason)

Docker-DCO-1.1-Signed-off-by: Andrew Page <admwiggin@gmail.com> (github: tianon)
Merge pull request #3740 from tianon/fix-mflag-dyntest

Fix mflag test issue with "ResetForTesting"
no more TODO

Docker-DCO-1.1-Signed-off-by: Victor Vieux <victor.vieux@docker.com> (github: vieux)
Merge pull request #3742 from vieux/update_todo

no more TODO