Don't generate quitquitquit files when running unit tests.

subprocess_unittest.cc

 // Copyright (c) 2010 The Chromium OS Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include <sys/stat.h>
 #include <sys/types.h>
 #include <unistd.h>
 #include <string>
 #include <vector>
 #include "base/string_util.h"
@@ skipping 76 matching lines @@
   Subprocess::Get().CancelExec(tag);
   return FALSE;
 }
 }  // namespace {}
 
 gboolean ExitWhenDone(gpointer data) {
   CancelTestData* cancel_test_data = reinterpret_cast<CancelTestData*>(data);
   if (cancel_test_data->spawned && !Subprocess::Get().SubprocessInFlight()) {
     // tear down the sub process
     printf("tear down time\n");
-    int status =
-        System(StringPrintf("wget http://127.0.0.1:%d/quitquitquit",
-                            kLocalHttpPort));
+    int status = System(
+        StringPrintf("wget -O /dev/null http://127.0.0.1:%d/quitquitquit",
+                     kLocalHttpPort));
     EXPECT_NE(-1, status) << "system() failed";
     EXPECT_TRUE(WIFEXITED(status))
         << "command failed to run or died abnormally";
     g_main_loop_quit(cancel_test_data->loop);
     return FALSE;
   }
   return TRUE;
 }
 
 TEST(SubprocessTest, CancelTest) {
   GMainLoop *loop = g_main_loop_new(g_main_context_default(), FALSE);
   CancelTestData cancel_test_data;
   cancel_test_data.spawned = false;
   cancel_test_data.loop = loop;
   g_timeout_add(100, &StartAndCancelInRunLoop, &cancel_test_data);
   g_timeout_add(10, &ExitWhenDone, &cancel_test_data);
   g_main_loop_run(loop);
   g_main_loop_unref(loop);
   printf("here\n");
 }
 
 }  // namespace chromeos_update_engine