Add boilerplate comments for inline unit test harness

Change-Id: Ie9b727ba8e4a2f9733ec9d5e183da9ebcd5b4071
diff --git a/drivers/NetgearXSM.py b/drivers/NetgearXSM.py
index b3241d5..f8ba8a5 100644
--- a/drivers/NetgearXSM.py
+++ b/drivers/NetgearXSM.py
@@ -664,6 +664,10 @@
 
 if __name__ == "__main__":
 
+    # Simple test harness - exercise the main working functions above to verify
+    # they work. This does *NOT* test really disruptive things like "save
+    # running-config" and "reload" - test those by hand.
+
     import optparse
 
     switch = 'vlandswitch05'