Comment 6 for bug 1536479

Just another point:
In neutronclient, where ever we have defined action=append, there is a check (if clause ) in the args2body
Example:
https://github.com/openstack/python-neutronclient/blob/master/neutronclient/neutron/v2_0/fw/firewall.py#L72

This is missing in the current code for subnetpool