devserver: start using payload scripts bundled with devserver

This follows CL's which move payload generators to devutils, and
removes the dependency on these scripts in src/scripts.

Following this, the autogeneration of payloads by the devserver
installed in chroot should work.

BUG=chromium-os:5246
TEST=cros_au_test_harness

Change-Id: Id3be5e140e93ee1813849f6ede6bbac53c60dde4

Review URL: http://codereview.chromium.org/6542009
diff --git a/autoupdate.py b/autoupdate.py
index 68aaba3..e560492 100644
--- a/autoupdate.py
+++ b/autoupdate.py
@@ -243,7 +243,7 @@
     _LogMessage('Generating update image %s' % update_path)
 
     update_command = [
-        '%s/cros_generate_update_payload' % self.scripts_dir,
+        '%s/cros_generate_update_payload' % self.devserver_dir,
         '--image="%s"' % image_path,
         '--output="%s"' % update_path,
         '--noold_style',
@@ -275,7 +275,7 @@
     """
     output_gz = os.path.join(output_dir, STATEFUL_FILE)
     subprocess.check_call(
-        ['%s/cros_generate_stateful_update_payload' % self.scripts_dir,
+        ['%s/cros_generate_stateful_update_payload' % self.devserver_dir,
          '--image=%s' % image_path,
          '--output_dir=%s' % output_dir,
         ])