Added --multiversiononly option to image SHA1 population script

* A portion of files have bad SHA1 values due to re-upload bugs.
  This adds an option to just force updates for files with re-uploads.

Change-Id: I24bd9a8f19bafc3e794cf32c78ce7f720f302627
(cherry picked from commit d35063273c264d9991e0cc47decf6976ca5f2844)