* tune exec/ipfw backend

configs/conf-available/10-backend-exec-ipfw.conf

@@ -1,6 +1,8 @@
+# -q option stops a ipfw table add or delete from failing if the entry
+# already exists or is not present.
 [backend:exec-ipfw]
 load  = backend_exec.so
-ban   = /sbin/ipfw table <ID> add <IP>
-unban = /sbin/ipfw table <ID> delete <IP>
+ban   = /sbin/ipfw -q table <ID> add <IP>
+unban = /sbin/ipfw -q table <ID> delete <IP>
 timeout = 2
 shared = yes