Update autotest tests to use make -j where possible.

client/site_tests/audiovideo_V4L2/audiovideo_V4L2.py

 # 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.
 
 import glob, logging, os, re, stat, time
 
 from autotest_lib.client.bin import test
 from autotest_lib.client.common_lib import error, site_ui, utils
 
 class audiovideo_V4L2(test.test):
     version = 1
     preserve_srcdir = True
     v4l2_major_dev_num = 81
     v4l2_minor_dev_num_min = 0
     v4l2_minor_dev_num_max = 64
 
 
     def setup(self):
         # TODO(jiesun): make binary here when cross compile issue is resolved.
         os.chdir(self.srcdir)
-        utils.system("make clean")
-        utils.system("make")
+        utils.make('clean')
+        utils.make()
 
 
     def run_once(self, run_unit_tests=True, run_capture_tests=True,
                  run_default_capture_test=False, time=0,
                  assert_mandatory_controls=False):
 
         self.assert_mandatory_controls = assert_mandatory_controls
         self.find_video_capture_devices()
         time = time / len(self.v4l2_devices)
 
@@ skipping 170 matching lines @@
             if (not match or
                 int(match.group(1)) != width or
                 int(match.group(2)) != height or
                 match.group(3) != self.supported_formats[0] or
                 int(match.group(4)) < minfps):
                 raise error.TestError("capture test failed")
 
             # Run the test again with X display.
             option.append("--display")
             okay, stdout = self.run_v4l2_capture_test(False, option)