BUG/MINOR: lua: report the correct function name in an error message

"req_channel" was reported instead of "res_channel". This is harmless.
diff --git a/src/hlua.c b/src/hlua.c
index fb39dc1..084b7d5 100644
--- a/src/hlua.c
+++ b/src/hlua.c
@@ -2578,7 +2578,7 @@
 {
 	struct hlua_txn *s;
 
-	MAY_LJMP(check_args(L, 1, "req_channel"));
+	MAY_LJMP(check_args(L, 1, "res_channel"));
 	s = MAY_LJMP(hlua_checktxn(L, 1));
 
 	if (!hlua_channel_new(L, s->s, s->s->rep))