Make dolphinviewtest_columns more stable.

Make dolphinviewtest_columns more stable.

Up to now, some Columns View tests that need a folder to be displayed
in the view only passed if they were run first: The first test always
passed, and if a test name was passed on the command line, such that
only this test would be run, this test would work as well. In other
cases, the view was empty, not showing the items in the folder.

The problem is worked around by creating a new DolphinView before each
test in the case of the Columns View. Added a TODO comment to make me
remember to look into this again at some point.

svn path=/trunk/KDE/kdebase/apps/; revision=1217260