releasetools: Fix a broken test due to verity utils relocation.

Test: python -m unittest test_validate_target_files
Change-Id: I2267e18f63d4a36ecd5fff911848470a860ab6cf
diff --git a/tools/releasetools/test_validate_target_files.py b/tools/releasetools/test_validate_target_files.py
index 7b29ef8..d778d11 100644
--- a/tools/releasetools/test_validate_target_files.py
+++ b/tools/releasetools/test_validate_target_files.py
@@ -20,9 +20,9 @@
 import os.path
 import shutil
 
-import build_image
 import common
 import test_utils
+import verity_utils
 from validate_target_files import ValidateVerifiedBootImages
 
 
@@ -109,7 +109,7 @@
   def _generate_system_image(self, output_file):
     verity_fec = True
     partition_size = 1024 * 1024
-    image_size, verity_size = build_image.AdjustPartitionSizeForVerity(
+    image_size, verity_size = verity_utils.AdjustPartitionSizeForVerity(
         partition_size, verity_fec)
 
     # Use an empty root directory.
@@ -132,7 +132,7 @@
         'verity_signer_cmd' : 'verity_signer',
         'verity_size' : str(verity_size),
     }
-    build_image.MakeVerityEnabledImage(output_file, verity_fec, prop_dict)
+    verity_utils.MakeVerityEnabledImage(output_file, verity_fec, prop_dict)
 
   def test_ValidateVerifiedBootImages_systemImage(self):
     input_tmp = common.MakeTempDir()