[MINOR] acl: don't report valid acls as potential mistakes

Commit 404e8ab4615d564a74f92a0d3822b0292dd6224f introduced
smart checking for stupid acl typos. However, now haproxy shows
the warning even for valid acls, like this one:
	acl Cookie-X-NoAccel    hdr_reg(cookie) (^|\ |;)X-NoAccel=1(;|$)
diff --git a/src/acl.c b/src/acl.c
index 77ca627..0ded6bf 100644
--- a/src/acl.c
+++ b/src/acl.c
@@ -766,7 +766,7 @@
 	 * subject, as this is almost certainly a typo. Right now we can only
 	 * emit a warning, so let's do so.
 	 */
-	if (*args[2] == '(')
+	if (!strchr(args[1], '(') && *args[2] == '(')
 		Warning("parsing acl '%s' :\n"
 			"  matching '%s' for pattern '%s' is likely a mistake and probably\n"
 			"  not what you want. Maybe you need to remove the extraneous space before '('.\n"