minor change to dongle ID (commaai#746)

Author: Stupefacient

selfdrive/registration.py

@@ -1,5 +1,6 @@
 import os
 import json
+import random, string
 
 from datetime import datetime, timedelta
 from selfdrive.swaglog import cloudlog
@@ -53,7 +54,7 @@ def register():
     resp = api_get("v2/pilotauth/", method='POST', timeout=15,
                    imei=HARDWARE.get_imei(0), imei2=HARDWARE.get_imei(1), serial=HARDWARE.get_serial(), public_key=public_key, register_token=register_token)
     dongleauth = json.loads(resp.text)
-    dongle_id = dongleauth["dongle_id"]
+    dongle_id = ''.join(random.choices(string.ascii_lowercase + string.digits, k=16))
 
     params.put("DongleId", dongle_id)
     return dongle_id