Return the right exit code in the runtest script

git-svn-id: svn://svn.iws.uni-stuttgart.de/DUMUX/dumux/trunk@15134 2fb0f335-1f38-0410-981e-8018bf24f1b0

bin/runtest.py

@@ -35,7 +35,7 @@ except OSError as e:
     print("OSError: Command not found. Most likely the executable specified doesn't exist.")
     sys.exit(1)
 if res:
-    sys.exit(1)
+    sys.exit(res)
 
 # run the comparison
 if args['script']: