Fix rejoining a room after hangup
Fix rejoining a room after hangup

The roomName was being reset in the render() call, and only reset when
text changed. The result was clicking the join button after hanging up
led to attempting to join the room "".

The roomName is now saved in the component state instead.

jitsi/jitsi-meet-react,jitsi/jitsi-meet-react,jitsi/jitsi-meet-react,jitsi/jitsi-meet-react