"connection.donotJoin" added.

`connection.donotJoin` added:

```javascript
connection.onstatechange =
function (state) {
    if(state == 'room-not-available') {

connection.donotJoin(connection.sessionid);
    }
};
```

You can use
`donotJoin` in following cases:

1. If `onstatechange` indicated that
room isn't available.
2. If you invoked `connection.join` but you didn't
yet allowed the camera.
3. If you invoked `connection.join` and you
allowed the camera but you quickly changed your mind to not join the
session.

When you'll invoke `connection.donotJoin`, RTCMultiConnection
will NEVER send participation request to the initiator. Without
participation request, you can't join a session.