fix(conference): disconnect on VIDEOBRIDGE_NOT_AVAILABLE error

Will disconnect on ConferenceErrors.VIDEOBRIDGE_NOT_AVAILABLE.
Show the same message when either JVB is not available or Jicofo
disconnects.

conference.js

             }
             break;
 
-        case ConferenceErrors.VIDEOBRIDGE_NOT_AVAILABLE:
-            APP.UI.notifyBridgeDown();
-            break;
-
             // not enough rights to create conference
         case ConferenceErrors.AUTHENTICATION_REQUIRED:
             // schedule reconnect to check if someone else created the room
             }
             break;
 
+            // FIXME FOCUS_DISCONNECTED is confusing event name.
+            // What really happens there is that the library is not ready yet,
+            // because Jicofo is not available, but it is going to give
+            // it another try.
         case ConferenceErrors.FOCUS_DISCONNECTED:
             {
                 let [focus, retrySec] = params;
             break;
 
         case ConferenceErrors.FOCUS_LEFT:
+        case ConferenceErrors.VIDEOBRIDGE_NOT_AVAILABLE:
+            // FIXME the conference should be stopped by the library and not by
+            // the app. Both the errors above are unrecoverable from the library
+            // perspective.
             room.leave().then(() => connection.disconnect());
-            APP.UI.notifyFocusLeft();
+            APP.UI.notifyVideoConferencingNotAvailable();
             break;
 
         case ConferenceErrors.CONFERENCE_MAX_USERS:

lang/main.json

         "detectext": "Error when trying to detect desktopsharing extension.",
         "failtoinstall": "Failed to install desktop sharing extension",
         "failedpermissions": "Failed to obtain permissions to use the local microphone and/or camera.",
-        "bridgeUnavailable": "Jitsi Videobridge is currently unavailable. Please try again later!",
-        "jicofoUnavailable": "Jicofo is currently unavailable. Please try again later!",
+        "serviceUnavailableMsg": "The video conferencing service is currently unavailable. Please try again later!",
         "maxUsersLimitReached": "The limit for maximum number of participants in the conference has been reached. The conference is full. Please try again later!",
         "lockTitle": "Lock failed",
         "lockMessage": "Failed to lock the conference.",

modules/UI/UI.js

     messageHandler.openDialog(title, reason, true, {}, () => false);
 };
 
-/**
- * Notify user that Jitsi Videobridge is not accessible.
- */
- UI.notifyBridgeDown = function () {
-    messageHandler.showError("dialog.error", "dialog.bridgeUnavailable");
-};
-
 /**
  * Show chat error.
  * @param err the Error
 };
 
 /**
- * Notify user that focus left the conference so page should be reloaded.
+ * Notify the user that the video conferencing service is badly broken and
+ * the page should be reloaded.
  */
-UI.notifyFocusLeft = function () {
+UI.notifyVideoConferencingNotAvailable = function () {
     let title = APP.translation.generateTranslationHTML(
         'dialog.serviceUnavailable'
     );
     let msg = APP.translation.generateTranslationHTML(
-        'dialog.jicofoUnavailable'
+        'dialog.serviceUnavailableMsg'
     );
     messageHandler.openDialog(
         title,