Upgrade neutron to allow multiple api processes.

Upgrade neutron to pick up a recent backport to havana,
which allows running multiple neutron-server worker
processes.

This is desirable, because clients have been observed
to timeout talking to neutron-server when several requests
are sent in close succession.
Merge pull request #226 from blueboxgroup/neutron-api-workers

Upgrade neutron to allow multiple api processes.