fix: Avoids storing lobby room instance in the main room object.
fix: Avoids storing lobby room instance in the main room object.

We sometimes see "error   Top-level error, please report:
                  /usr/lib/prosody/util/serialization.lua:38: Can't serialize table: table has multiple references".
This also slows down restarting prosody.

jitsi/jitsi-meet,jitsi/jitsi-meet,gpolitis/jitsi-meet,gpolitis/jitsi-meet,jitsi/jitsi-meet,gpolitis/jitsi-meet,jitsi/jitsi-meet,gpolitis/jitsi-meet,gpolitis/jitsi-meet,gpolitis/jitsi-meet,jitsi/jitsi-meet,jitsi/jitsi-meet,jitsi/jitsi-meet,gpolitis/jitsi-meet,jitsi/jitsi-meet,gpolitis/jitsi-meet