monitor: fix missing space after chain name

Due to change f3ff9e9 ("rule: delete extra space in rule indentation") in function rule_print(), a missing space happens in monitor.

before this patch:
% nft monitor
add rule ip test-table test-chainip protocol tcp

after this patch:
% nft monitor
add rule ip test-table test-chain ip protocol tcp

---
 src/netlink.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

index f957295..c118502 100644
@@ -1869,7 +1869,7 @@ static int netlink_events_rule_cb(const struct nlmsghdr *nlh, int type,
 			r = netlink_delinearize_rule(monh->ctx, nlr);
 			nlr_for_each_set(nlr, rule_map_decompose_cb, NULL);
 
-			printf("add rule %s %s %s", family, table, chain);
+			printf("add rule %s %s %s ", family, table, chain);
 			rule_print(r);
 			printf("\n");
 

Applied, thanks Arturo.