Bug - Change User Roles

[cruizba]

Deployment info

OpenVidu Teaching version: master - 11459a6
Docker Image: openvidu/openviduteaching:1.3.0-beta1
We've built or own docker image by executing ./create_image.sh in https://github.com/codeurjc-students/2019-OpenViduTeaching/tree/master/docker in order to update OpenVidu Client version to 2.15.0.

Issue description:

After a user enters a room with an invitation link, the role can't be changed for this user. It would be great to have a control panel to edit rooms and users.