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"