Replace oslo_utils.timeutils.isotime
Replace oslo_utils.timeutils.isotime

oslo_utils.timeutils.isotime is deprecated in version '1.6', use
common_utils.isotime instead.

Change-Id: Iad9f41fb7d88a1bee2ca0d0b488ba66856e82bec
Closes-Bug: #1514331

openstack/senlin,stackforge/senlin,openstack/senlin,openstack/senlin,stackforge/senlin