Check for "buildbot" user in IsAutomaticTest().

The new buildbot setup runs the code under this user, so adjust the check for
running under buildbot to detect it.

tests/test.cpp

@@ -467,7 +467,7 @@ extern bool IsAutomaticTest()
             username = wxGetUserId();
 
         username.MakeLower();
-        s_isAutomatic = username.Matches("buildslave*") ||
+        s_isAutomatic = username == "buildbot" ||
                             username.Matches("sandbox*");
     }