roles/common: Use individual calls with firewalld

Seems to work around an issue when firewalld is using the nftables
backend with iptables 1.8.2 on Debian 10. Alternatively I could go
back to using the iptables backend... hmm.

See: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=914694

roles/common/tasks/firewall_Debian.yml

@@ -17,6 +17,18 @@
     notify:
       - restart firewalld
 
+# firewalld seems to have an issue with iptables 1.8.2 when using the nftables
+# backend. Using individual calls seems to work around it.
+# See: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=931722
+  - name: Use individual iptables calls
+    when: ansible_distribution_major_version is version_compare('10', '>=')
+    lineinfile:
+      dest: /etc/firewalld/firewalld.conf
+      regexp: '^IndividualCalls=no$'
+      line: 'IndividualCalls=yes'
+    notify:
+      - restart firewalld
+
   - name: Copy firewalld public zone file
     when: ansible_distribution_major_version is version_compare('8', '>=')
     template: src=public.xml.j2 dest=/etc/firewalld/zones/public.xml owner=root mode=0600