fwaas v2 installation with devstack set the wrong plugin class path in neutron.conf

[zhaobo]

This issue will be hit during devstack installation if we use q-fwaas-v2.
The neutron.conf genarated automaticly will set the fwaas v2 service
plugin with the wrong class path.

neutron.conf
-------
[DEFAULT]
.....
service_plugins = neutron_fwaas.services.firewall.fwaas_plugin_v2.FirewallPluginV2

endpoint.txt
-------
[neutron.service_plugins]
firewall = neutron_fwaas.services.firewall.fwaas_plugin:FirewallPlugin
firewall_v2 = neutron_fwaas.services.firewall.fwaas_plugin_v2:FirewallPluginV2
neutron.services.firewall.fwaas_plugin.FirewallPlugin = neutron_fwaas.services.firewall.fwaas_plugin:FirewallPlugin

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/386501

[OpenStack Infra (hudson-openstack)]

Change abandoned by ZhaoBo (<email address hidden>) on branch: master
Review: https://review.openstack.org/386501