Updated openstack/openstack
Project: openstack/taskflow  ccec06043d1db66ac537836adbbb2de30dd4dae1

Use timeutils functions instead of misc.wallclock

The common oslo timeutils functions can perform the
same time methods using the better datetime objects than
using the raw unix timestamps directly, so in order to
reduce a little bit of code just use the functions that
module provides instead of our own.

Also adds a few more tests that validate the various runtime
errors being thrown to ensure they are thrown when expected
and handles the case where time goes backwards (say when ntpd
updates) in a more reliable manner (by not becoming negative).

Change-Id: I6153ff8379833844105545ddb21dede65a7d4d3a