Fix some spelling errors in net_helpers.py
Fix some spelling errors in net_helpers.py

Change-Id: I92b552dfcd18ce41cfe70203242b86d2e4f6a46c

mahak/neutron,eayunstack/neutron,cloudbase/neutron,huntxu/neutron,openstack/neutron,openstack/neutron,eayunstack/neutron,cloudbase/neutron,sebrandon1/neutron,mahak/neutron,openstack/neutron,noironetworks/neutron,igor-toga/local-snat,mahak/neutron,noironetworks/neutron,huntxu/neutron,sebrandon1/neutron,igor-toga/local-snat