panel: Make Animation visible by default

None of the other widget actors hide themselves by default;
that's a GTK+ thing.

js/ui/unlockDialog.js

@@ -172,7 +172,6 @@ const UnlockDialog = new Lang.Class({
 
         this._workSpinner = new Panel.AnimatedIcon('process-working.svg', LoginDialog.WORK_SPINNER_ICON_SIZE);
         this._workSpinner.actor.opacity = 0;
-        this._workSpinner.actor.show();
 
         this.allowCancel = false;
         this.buttonLayout.visible = true;