TargetSetupWidget: Do not always pre-expand selected kits

Does not add much value (anymore), except in the import case.
Expanded targets take away a lot of space, pushing other targets
or potential kits out of the visible area

Change-Id: Iff0c46643b0fccef7e272a036d0c9c3a099ccc1f
Reviewed-by: Daniel Teske <daniel.teske@digia.com>