xep_0454: also include finalize's result in the payload

Signed-off-by: Maxime “pep” Buquet <pep@bouah.net>

slixmpp/plugins/xep_0454/__init__.py

@@ -67,8 +67,7 @@ class XEP_0454(BasePlugin):
                 break
             payload += aes_gcm.update(buf)
 
-        aes_gcm.finalize()
-        payload += aes_gcm.tag
+        payload += aes_gcm.finalize() + aes_gcm.tag
         fragment = aes_gcm_iv.hex() + aes_gcm_key.hex()
         return (payload, fragment)