[JUNIT] cleaned up SarosSessionTest

Change-Id: I34ad63c1a17f29e6d0fe352136341e8eef673559
Reviewed-on: http://saros-build.imp.fu-berlin.de/gerrit/1733
Tested-by: Saros-Eclipse QA
Tested-by: Jenkins CI
Reviewed-by: Stefan Rossbach <srossbach@arcor.de>