TT#70901 selenium: update on "only use one thread for local testruns"

yeah... the threads were changed on jenkins side, not on locals one.
fixing that now

Change-Id: Ibf9b454ee58437c3eda2e8fb0bcc887ffea3ff32

t/selenium/testrunner

@@ -63,7 +63,7 @@ if [ "${OUTPUT_TYPE:-}" = "junit" ] ; then
   RC="${PIPESTATUS[0]}"
 else
   #Change thread count here and in nose2cfg/localtest.cfg
-  export THREADS=2
+  export THREADS=1
   python3 testrun.py -v -c nose2cfg/localtest.cfg|| RC=$?
 fi