Update python-neutronclient version to 2.3.3

Current update is required by the heat neutron-metering-resources:

https://blueprints.launchpad.net/heat/+spec/neutron-metering-resources

Change-Id: I7a7534523cd5185a2b9f02271774b7284c640bab
Merge "Update python-neutronclient version to 2.3.3"
Merge commit 'refs/changes/81/68181/1' of git://gold.eng.hq.xensource.com/git/github/openstack/requirements into tmpbranch