Add logs for update_engine and image_to_live to test artifacts.

bin/au_test_harness/au_test.py

Index: bin/au_test_harness/au_test.py
diff --git a/bin/au_test_harness/au_test.py b/bin/au_test_harness/au_test.py
index 076aca0a4fc0f5f245a5e8e7ec67b162fca1ea86..c0a7de3264ce3e8b71cbcaa1d5543e8420d11447 100644
--- a/bin/au_test_harness/au_test.py
+++ b/bin/au_test_harness/au_test.py
@@ -58,12 +58,16 @@ class AUTest(unittest.TestCase):
     elif not os.path.exists(cls.target_image_path):
       cros_lib.Die('%s does not exist' % cls.target_image_path)
 
-    # Initialize test root.
+    # Initialize test root.  Test root path must be in the chroot.
     if not cls.test_results_root:
       if options.test_results_root:
+        assert 'chroot/tmp' in options.test_results_root, \
+          'Must specify a test results root inside tmp in a chroot.'
         cls.test_results_root = options.test_results_root
       else:
-        cls.test_results_root = tempfile.mkdtemp(prefix='au_test_harness')
+        cls.test_results_root = tempfile.mkdtemp(
+            prefix='au_test_harness',
+            dir=cros_lib.PrependChrootPath('/tmp'))
 
       cros_lib.Info('Using %s as the test results root' % cls.test_results_root)