Use gtest_filter syntax in jstest filter

run_jstests.py

Index: run_jstests.py
diff --git a/run_jstests.py b/run_jstests.py
index 294d9b6232c2c04baab9bb62a842b7c537306d69..567253ba7a5f084c140cb9e76b21329e6c49ebc8 100755
--- a/run_jstests.py
+++ b/run_jstests.py
@@ -27,7 +27,7 @@ except:
 
 def main(argv):
   parser = argparse.ArgumentParser()
-  parser.add_argument('--filter', help='Only tests that match this pattern will be run.')
+  parser.add_argument('--filter', help='See gtest_filter syntax.')
   parser.add_argument('--debug_level', help='Verbosity level of debug messages.')
   parser.add_argument('--no_console_log',
       action='store_true', help='Disable the console log output.')