DPP: Fix memory leak on dpp_auth_build_conf() error paths

The wpabuf for the message needs to be freed on the error paths.

Signed-off-by: Jouni Malinen <jouni@qca.qualcomm.com>

src/common/dpp.c

@@ -3248,6 +3248,7 @@ skip_wrapped_data:
 	return msg;
 
 fail:
+	wpabuf_free(msg);
 	return NULL;
 }