assign hub in token app

avoids AttributeError on hub if there are
users with running servers.

Don't call init_hub,
which can modify the Hub's entries in the database,
which shouldn't happen in the token command.

jupyterhub/app.py

@@ -126,6 +126,7 @@ class NewToken(Application):
         hub = JupyterHub(parent=self)
         hub.load_config_file(hub.config_file)
         hub.init_db()
+        hub.hub = hub.db.query(orm.Hub).first()
         hub.init_users()
         user = orm.User.find(hub.db, self.name)
         if user is None: