I have sent an email to the build system SIG which proposes to remove the CATKIN_TEST_RESULTS_DIR environment variable.
Since it might have wide impact I want to mention it on this list too to make users aware of the planned change.

If you are interested in the details, the discussion and / or are relying on the environment variable please read / comment on the SIG mailing list:

https://groups.google.com/forum/#!topic/ros-sig-buildsystem/suBvWzoGODU

Thank you,
- Dirk