CI fix : Cleanup

testssl.sh worked as expected.
Under the hood, broken pipes are expected as part of the fast loop exit
strategy that relies as little as possible on timeout detection.
But under the CI, testssl.sh output is garbled by the subshells stderr
outputs, catched for some reason by 'prove -v'.
Simply redirecting the stderr output of the offending command to
/dev/null fixes the problem.

testssl.sh

@@ -17173,11 +17173,6 @@ run_renego() {
           prln_warning "not having provided client certificate and private key file, the client x509-based authentication prevents this from being tested"
           fileout "$jsonID" "WARN" "not having provided client certificate and private key file, the client x509-based authentication prevents this from being tested"
      else
-#          # We will extensively use subshell and command pipe
-#          # Do not let herited pipeline error control interfere
-#          [[ $- == *e* ]] && restore_pipeerror=1 
-#          [[ $restore_pipeerror == 1 ]] && set +e
-#	  set +o pipefail
           # We will need $ERRFILE for mitigation detection
           if [[ $ERRFILE =~ dev.null ]]; then
                ERRFILE=$TEMPDIR/errorfile.txt || exit $ERR_FCREATE
@@ -17288,7 +17283,6 @@ run_renego() {
                        ;;
                esac
           fi
-#          [[ $restore_pipeerror == 1 ]] && set -e
      fi
 
      #pr_bold " Insecure Client-Initiated Renegotiation  "  # pre-RFC 5746, CVE-2009-3555