paycheck: Update generated protobuf code.

This patch updates the generated update_metadata_pb2.py file with the
latest changes in the udpate_metadata.proto file. Some other changes in
the update_payload library were required to match the changes in the
.proto file.

BUG=b:23179128
TEST=paycheck unittests

Change-Id: I482d67d4a35f69438a26395eea77286994108b7a
Reviewed-on: https://chromium-review.googlesource.com/299498
Commit-Ready: Alex Deymo <deymo@chromium.org>
Tested-by: Alex Deymo <deymo@chromium.org>
Reviewed-by: Gilad Arnold <garnold@chromium.org>
diff --git a/scripts/update_payload/test_utils.py b/scripts/update_payload/test_utils.py
index 4e7881d..8746fce 100644
--- a/scripts/update_payload/test_utils.py
+++ b/scripts/update_payload/test_utils.py
@@ -8,6 +8,7 @@
 
 import cStringIO
 import hashlib
+import os
 import struct
 import subprocess
 
@@ -21,8 +22,10 @@
 
 
 # Private/public RSA keys used for testing.
-_PRIVKEY_FILE_NAME = 'payload-test-key.pem'
-_PUBKEY_FILE_NAME = 'payload-test-key.pub'
+_PRIVKEY_FILE_NAME = os.path.join(os.path.dirname(__file__),
+                                  'payload-test-key.pem')
+_PUBKEY_FILE_NAME = os.path.join(os.path.dirname(__file__),
+                                 'payload-test-key.pub')
 
 
 def KiB(count):