fix(JitsiConference) simplify auth-and-upgrade procedure

It's not necessary to perform a full join, sending a conference IQ is
enough.

authenticateAndUpgradeRole.js

  * @param {string} options.id - XMPP user's ID to log in. For example,
  * user@xmpp-server.com.
  * @param {string} options.password - XMPP user's password to log in with.
- * @param {string} [options.roomPassword] - The password to join the MUC with.
  * @param {Function} [options.onLoginSuccessful] - Callback called when logging
  * into the XMPP server was successful. The next step will be to obtain a new
  * session ID from Jicofo and join the MUC using it which will effectively
 
     // 2. Let the API client/consumer know as soon as the XMPP user has been
     //    successfully logged in.
-    onLoginSuccessful,
-
-    // 3. Join the MUC.
-    roomPassword
+    onLoginSuccessful
 }) {
     let canceled = false;
     let rejectPromise;
                         }
 
                         // At this point we should have the new session ID
-                        // stored in the settings. Jicofo will allow to join the
-                        // room.
-                        this.join(roomPassword);
+                        // stored in the settings. Send a new conference IQ.
+                        this.room.moderator.allocateConferenceFocus();
 
                         resolve();
                     })

types/auto/authenticateAndUpgradeRole.d.ts

  * @param {string} options.id - XMPP user's ID to log in. For example,
  * user@xmpp-server.com.
  * @param {string} options.password - XMPP user's password to log in with.
- * @param {string} [options.roomPassword] - The password to join the MUC with.
  * @param {Function} [options.onLoginSuccessful] - Callback called when logging
  * into the XMPP server was successful. The next step will be to obtain a new
  * session ID from Jicofo and join the MUC using it which will effectively
  * thenable will be rejected with an empty object (i.e. no error property will
  * be set on the rejection reason).
  */
-export default function authenticateAndUpgradeRole({ id, password, onCreateResource, onLoginSuccessful, roomPassword }: {
+export default function authenticateAndUpgradeRole({ id, password, onCreateResource, onLoginSuccessful }: {
     id: string;
     password: string;
-    roomPassword?: string;
     onLoginSuccessful?: Function;
 }): any;
 export type UpgradeRoleError = {