common/iptables: add some ||true as needed

Signed-off-by: Mattia Rizzolo <mapreri@ubuntu.com>

roles/common/templates/firewall/firewall.sh

@@ -50,15 +50,15 @@ for arg; do
 done
 
 # Reset the firewall
-command -D INPUT -j input 2>/dev/null  # Remove firewall's input chain
+command -D INPUT -j input 2>/dev/null || true  # Remove firewall's input chain
 
 # Flush chains
 for chain in "${CHAINS[@]}"; do
-    command -F "${chain}" 2>/dev/null
+    command -F "${chain}" 2>/dev/null || true
 done
 # Delete chains -- must be done after because of references
 for chain in "${CHAINS[@]}"; do
-    command -X "${chain}" 2>/dev/null
+    command -X "${chain}" 2>/dev/null || true
 done
 
 echo "Existing firewall configuration cleaned up"