[TECH SUPPORT] LPS-51097 Keep defaulting to public pages in Control Panel

Hey Julio,

It turned out that the original commit of this LPS caused a behavior change: when you go to Admin -> Pages, "tabs1" is not set (and themeDisplay.getLayoutSet() is the layoutSet of the Control Panel group which is private) so now it shows the private tab by default. I have changed the code to keep the original behavior.

Please review the changes.

Thanks,
Ákos