REVIEW:122834: Fix a workspace restoration bug.

This patch fixes the problem that can be seen in this video:
http://lyzo.eu/f/20150304/workspace_restore_bug.mkv Notice the color
selection box getting too tall when switching from "VFX_Paint" to "MM_02"
(you can see how it "bounces") This also happens in other configurations
with other dockers.

Hiding all dockers before restoring them fixes the issue.

Patch by Moritz Molch. Thanks!
CCMAIL:kde@moritzmolch.de