CLEANUP: lua: bad error messages

An error message reference "register_service" in place of
"register_action".

This one should be backported to 1.6.
diff --git a/src/hlua.c b/src/hlua.c
index ccee755..d70b01b 100644
--- a/src/hlua.c
+++ b/src/hlua.c
@@ -6101,7 +6101,7 @@
 	int len;
 	struct hlua_function *fcn;
 
-	MAY_LJMP(check_args(L, 3, "register_service"));
+	MAY_LJMP(check_args(L, 3, "register_action"));
 
 	/* First argument : converter name. */
 	name = MAY_LJMP(luaL_checkstring(L, 1));