[FIX] commons/Dialog: Hide DOM content after closing the PopUp

This change makes the popup render its content as hidden and only
shows it when opening the popup. It hides it again on close.

Change-Id: If37a2772925b9da3b0cba1e9549787d3aeea47d9
Merge "[FIX] commons/Dialog: Hide DOM content after closing the PopUp"