config: Set the list separator to be comma

The code did not set the list separator so semicolon was used by
default. The documentation in config-format.txt says the list
items are separated by comma.

src/config.c

@@ -720,6 +720,8 @@ static int load_config(struct connman_config *config)
 	if (!keyfile)
 		return -EIO;
 
+	g_key_file_set_list_separator(keyfile, ',');
+
 	/* Verify keys validity of the global section */
 	check_keys(keyfile, "global", config_possible_keys);