Prepend an initial flush to the saved nftables ruleset

ansible/roles/nftables/tasks/main.yml

@@ -51,8 +51,8 @@
 
 - name: Install new nftables ruleset
   become: yes
-  copy:
-    content: "{{ nftables_ruleset_candidate.stdout ~ '\n' }}" # counter the automatic stripping
+  template:
+    src: nftables.conf
     dest: /etc/nftables.conf
     owner: root
     group: root

ansible/roles/nftables/templates/nftables.conf

+flush ruleset
+
+{{ nftables_ruleset_candidate.stdout }}