Sync module timeutils from Oslo

Sync lastest module timeutils from Oslo. This patch includes fix of
some bugs and makes the module Python 3 compatible.
https://github.com/openstack/oslo-incubator/commits/master/openstack/common/timeutils.py

Part of blueprint py33

Change-Id: If340120077af1008282e500eaacfeb43aa3eb7e5
Merge "Sync module timeutils from Oslo"