Klipper config: set UI state when loading the same way as when editing

When "Keep the selection and clipboard the same" is unchecked, some widgets are disabled. But that was only applied when unchecking the checkbox after opening the dialog, not when the checkbox was initially (dialog loading time) unchecked due to settings. Now, widgets that should be disabled at dialog loading time are disabled.

(cherry picked from commit 1e25653e)