Bump Neutron version to use load balancer objects

 * Neutron v2 includes the load_balancer item, which points to the
   load_balancer URL

Change-Id: Iccbfd122c2f35b8cb0549b02417e7f4a2bdae9e6
Fixes: MN-2760
Signed-off-by: Ryu Ishimoto <ryu@midokura.com>