libnl3, xcp-python-libs: Use Source0: instead of Source:

Signed-off-by: Euan Harris <euan.harris@citrix.com>
openstack-xapi-plugins: Remove package

We don't need to carry this package as anyone
wanting to run OpenStack can install the plugins
from upstream, for example by using devstack.

Signed-off-by: Euan Harris <euan.harris@citrix.com>
Merge pull request #548 from euanh/build-improvements

Build improvements