Used wrong registration id and identity key when building a session

updates #497

src/converse-omemo.js

@@ -172,8 +172,8 @@
                           prekey = device.getRandomPreKey();
 
                     return sessionBuilder.processPreKey({
-                        'registrationId': parseInt(_converse.omemo_store.get('device_id'), 10),
-                        'identityKey': u.base64ToArrayBuffer(_converse.omemo_store.get('identity_key')),
+                        'registrationId': parseInt(device.get('id'), 10),
+                        'identityKey': u.base64ToArrayBuffer(bundle.identity_key),
                         'signedPreKey': {
                             'keyId': bundle.signed_prekey.id, // <Number>
                             'publicKey': u.base64ToArrayBuffer(bundle.signed_prekey.public_key),