SingleFeatureTest (SFT) karaf.log should be kept outside the temporary PAX Exam to be preserved for analysis

During today's Kernel Projects call, when I inquired how we could make progress on the latest "Build timed out (after 120 minutes). Marking the build as failed." in integration/distribution's odl-integration-all, e.g. here, for (c/70354), rovarga pointed out that the main problem is that we have no visibility in the karaf.log in case of such failures.

skitt had tried to keep the Pax Exam output, but that blew up disk usage.

We could try to make SFT log somewhere else in /target that is kept in builds.