Fix timeout in ctkPathListWidgetWithButtonsTest with Qt 4.6.3

The thread was deleted and the singleshot was not executed before the
dialog was closed.
Closes #340
Merge branch '340-ctkpathlistwidgetwithbuttonstester-timeout'

* 340-ctkpathlistwidgetwithbuttonstester-timeout:
  Fix timeout in ctkPathListWidgetWithButtonsTest with Qt 4.6.3