au_test_harness: fix a function call, add sudo in front of ifconfig

Note: sudo before ifconfig is for running on distros which do not
have /sbin or /usr/sbin in common user's paths, like gentoo.

Change-Id: I85bd379ad059d6ecaa8c11f3167fae27987479dd

BUG=5246
TEST=run cros_au_test_harness and see it not fail

Review URL: http://codereview.chromium.org/6541008

bin/cros_au_test_harness.py

@@ -482,7 +482,7 @@ class RealAUTest(unittest.TestCase, AUTest):
 
   def PrepareBase(self, image_path):
     """Auto-update to base image to prepare for test."""
-    _PrepareRealBase(image_path)
+    self._PrepareRealBase(image_path)
 
   def _UpdateImage(self, image_path, src_image_path='', stateful_change='old',
                    proxy_port=None, private_key_path=None):

lib/cros_build_lib.py

@@ -256,8 +256,8 @@ def GetIPAddress(device='eth0'):
   this method gives you a generic way to get the address so you are reachable
   either via a VM or remote machine on the same network.
   """
-  ifconfig_output = RunCommand(['ifconfig', device], redirect_stdout=True,
-                               print_cmd=False)
+  ifconfig_output = RunCommand(['sudo', 'ifconfig', device],
+                               redirect_stdout=True, print_cmd=False)
   match = re.search('.*inet addr:(\d+\.\d+\.\d+\.\d+).*', ifconfig_output)
   if match:
     return match.group(1)