Updated openstack/openstack
Project: openstack/nova  6adcae8e5154ea3a69284b5304c605b0a50e0da9

xenapi plugins must target only Python 2.4 features

Add a comment documenting the restriction that our xenapi plugins must
target Python 2.4 features because of restrictions with the XenServer
dom0 userspace.

Change-Id: Ide130923b16c0555c3190cbd63ce97e18d18aae0