add 'runtime_params' to -help output

Author: etpalmer63

test_util.py

@@ -162,6 +162,9 @@
   runs_to_average = < number of past runs to include when computing the average,
                       default is 5 >
 
+  runtime_params =  < run-time parameters to be added to the test command line 
+                      arguments > 
+
 Getting started:
 
 To set up a test suite, it is probably easiest to write the