Test date with UTC instead of local timezone.

iso_format test uses local timezone so it can fail at certain times
of the day depending on which timezone the tests are run in.

Fixes bug 1139131

Change-Id: I8fe423d96c438b46a9307fe1ecf648707183ff1c
Merge "Test date with UTC instead of local timezone."
Merge remote-tracking branch 'm_src_repo/webob-issue' into build-temp