Fix vpnaas for neutron

1. Install the missing vpnaas python module in neutron-server Dockerfile
2. Remove duplicated neutron-lbaas-common package from neutron-server,
since it is installed in neutron-base
3. Fix service plugin config, it's not vpn`ass` ;)) 'vpnass' ->
'neutron_vpnaas.services.vpn.plugin.VPNDriverPlugin' [1]

[1]:
https://github.com/openstack/neutron-vpnaas/blob/stable/newton/devstack/settings#L8

Change-Id: I5250b6875d96ef5df9cf39bce10ce072982aa80d
Closes-bug: #1625020

ansible/roles/neutron/templates/neutron.conf.j2

@@ -35,7 +35,7 @@ host = {{ ansible_hostname }}_{{ item }}
 
 allow_overlapping_ips = true
 core_plugin = ml2
-service_plugins = router{% if enable_neutron_lbaas | bool %},neutron_lbaas.services.loadbalancer.plugin.LoadBalancerPluginv2{% endif %}{% if enable_neutron_qos | bool %},qos{% endif %}{% if enable_neutron_vpnaas | bool %},vpnass{% endif %}{% if neutron_plugin_agent == "sfc" %}flow_classifier,sfc{% endif %}
+service_plugins = router{% if enable_neutron_lbaas | bool %},neutron_lbaas.services.loadbalancer.plugin.LoadBalancerPluginv2{% endif %}{% if enable_neutron_qos | bool %},qos{% endif %}{% if enable_neutron_vpnaas | bool %},neutron_vpnaas.services.vpn.plugin.VPNDriverPlugin{% endif %}{% if neutron_plugin_agent == "sfc" %}flow_classifier,sfc{% endif %}
 
 {% if enable_neutron_agent_ha | bool %}
 dhcp_agents_per_network = {{ dhcp_agents_per_network }}

docker/neutron/neutron-server/Dockerfile.j2

@@ -9,15 +9,16 @@ MAINTAINER {{ maintainer }}
     {% if base_distro in ['centos', 'fedora', 'oraclelinux', 'rhel'] %}
 
         {% set neutron_server_packages = [
-            'openstack-neutron-lbaas'
+            'openstack-neutron-lbaas',
+            'openstack-neutron-vpnaas',
         ] %}
 
     {% elif base_distro in ['ubuntu'] %}
 
         {% set neutron_server_packages = [
-            'neutron-lbaas-common',
             'neutron-lbaasv2-agent',
-            'python-neutron-lbaas'
+            'python-neutron-lbaas',
+            'python-neutron-vpnaas',
         ] %}
 
     {% endif %}