Fixes missing boolean for Neutron FWaaS

The missing boolean breaks Neutron FWaaS deployment.

Change-Id: I169246a6ce8b15af76fd84b32029437016bd3c42
Closes-Bug: #1847562

ansible/roles/neutron/defaults/main.yml

@@ -358,7 +358,7 @@ neutron_rolling_upgrade_services: ["neutron", "neutron-fwaas", "neutron-vpnaas"]
 ####################
 service_plugins:
   - name: "firewall_v2"
-    enabled: "{{ enable_neutron_fwaas }}"
+    enabled: "{{ enable_neutron_fwaas | bool }}"
   - name: "flow_classifier"
     enabled: "{{ enable_neutron_sfc | bool }}"
   - name: "metering"