AU: Remove instances of Omaha ID -- machine ID and user ID.

Also add a unit test to make sure we are not sending machineid or userid
attributes.

BUG=1439
TEST=unit tests, gmerged on device, checked for update, looked at logs

Review URL: http://codereview.chromium.org/2808082
diff --git a/omaha_request_action.h b/omaha_request_action.h
index c5f4d19..6f30a32 100644
--- a/omaha_request_action.h
+++ b/omaha_request_action.h
@@ -145,7 +145,7 @@
   // be sent as pings to Omaha.
   void InitPingDays();
 
-  // Based on the perstitent preference store values, calculates the
+  // Based on the persistent preference store values, calculates the
   // number of days since the last ping sent for |key|.
   int CalculatePingDays(const std::string& key);