Fix description of ListSubnet
Fix description of ListSubnet

The help texts for both "neutron net-list" and "neutron subnet-list"
give the same text "List networks that belong to a given tenant."

Fix it so that subnet-list output the proper "subnet"

Change-Id: I0877b51ad10ac0e04b24effa7cbd1e412098e363
Partial-Bug: #1244618

huntxu/python-neutronclient,johnpbatty/python-neutronclient,rackerlabs/rackspace-python-neutronclient,sajuptpm/python-neutronclient-ipam,venusource/python-neutronclient,JioCloud/python-neutronclient,varunarya10/python-neutronclient,yamahata/python-tackerclient,Juniper/python-neutronclient,johnpbatty/python-neutronclient,NeCTAR-RC/python-neutronclient,cernops/python-neutronclient,Stavitsky/python-neutronclient,NeCTAR-RC/python-neutronclient,vijayendrabvs/ssl-python-neutronclient,mangelajo/python-neutronclient,openstack/python-neutronclient,rackerlabs/rackspace-python-neutronclient,cernops/python-neutronclient,openstack/python-neutronclient,roaet/python-neutronclient,noironetworks/python-neutronclient,cryptickp/python-neutronclient,varunarya10/python-neutronclient,cryptickp/python-neutronclient,venusource/python-neutronclient,roaet/python-neutronclient,noironetworks/python-neutronclient,Stavitsky/python-neutronclient,eayunstack/python-neutronclient,Juniper/python-neutronclient,sajuptpm/python-neutronclient-ipam,JioCloud/python-neutronclient,mangelajo/python-neutronclient,huntxu/python-neutronclient,yamahata/python-tackerclient,eayunstack/python-neutronclient,vijayendrabvs/ssl-python-neutronclient