Add test where a database is corrupted and the chatroom ends up with no participants other than me

Improve test where a conference information without chat capabilities is mistakenly associated to a chatroom. In such a case, the core will detect this at startup, delete the conference information and bring the chatrrom back to the Created state.

Associated conference information to a client conference only if there is an active session for it. On the server side, the conference information is attached since the start.

Improve checks on server conference information deletion at the end of a conference