Updated openstack/openstack
Project: openstack/nova  8e151e49a0f7ea6cbff6f32363b0860ad4237933

Update requirements to include decorator>=3.4.0

This third party package is used but there was no specific
requirement for it.

Change-Id: I50fcc7a1c4029b36e02e75eaf27df7ca791aef4e