Fix typo in neutron.gateway.cluster class

Change-Id: Ife40825482202b691e4aaade95c7c61e8c318199
diff --git a/neutron/gateway/cluster.yml b/neutron/gateway/cluster.yml
index 6d33684..2a4f4f4 100644
--- a/neutron/gateway/cluster.yml
+++ b/neutron/gateway/cluster.yml
@@ -18,7 +18,7 @@
       vlan_aware_vms: ${_param:neutron_enable_vlan_aware_vms}
       agent_mode: ${_param:neutron_gateway_agent_mode}
       backend:
-        tenant_network_types: ${_param:neutron_tenant_network_types}"
+        tenant_network_types: "${_param:neutron_tenant_network_types}"
       message_queue:
         port: ${_param:openstack_rabbitmq_port}
         members: