JCK Swing interactive test JScrollBarTest0013 fails with Nimbus and GTK L&Fs

The following JCK Swing interactive test fails with Nimbus and GTK L&Fs:
api/javax_swing/interactive/JScrollBarTests.html#JScrollBar[JScrollBarTest0013]

To reproduce the problem:
- Start the test using Nimbus or GTK L&F
- Click to the left of the scrollbar knob

This is expected to decrement the value of the scrollbar by 10, however
the value of the scrollbar is incremented by 10. Subsequent clicks to the
left of the scrollbar result in expected behavior, ie decrement of
scrollbar value by 10.

JCK8 b07
JDK8 b30
L&F: Nimbus, GTK
The problem is reproduced just once in the first time using the scrollbar. This is corrected description:

- Start the test using Nimbus or GTK L&F
- Click to the left of the scrollbar knob

This is expected to decrement the value of the scrollbar by 10, however
the value of the scrollbar is decremented to the begin of the scrollbar.