parallel_emerge/cros_mark_as_stable: fix CLEAN_DELAY handling

The UNMERGE_DELAY variable was last seen in the portage code base in
2006.  All current code I can find refers to CLEAN_DELAY, so change
parallel emerge to use the new variable name.

Further, improve cros_mark_as_stable to not wait 5 seconds when
cleaning out packages by setting CLEAN_DELAY.

BUG=None
TEST=`cbuildbot arm-tegra2-paladin` no longer shows delay count down

Change-Id: Id3c44f91c5f70ca4a59ee600ccfae14c8485758e
Reviewed-on: https://gerrit.chromium.org/gerrit/29303
Reviewed-by: David James <davidjames@chromium.org>
Commit-Ready: Mike Frysinger <vapier@chromium.org>
Tested-by: Mike Frysinger <vapier@chromium.org>
diff --git a/scripts/parallel_emerge.py b/scripts/parallel_emerge.py
index 6f4e45f..33a3223 100644
--- a/scripts/parallel_emerge.py
+++ b/scripts/parallel_emerge.py
@@ -1,5 +1,5 @@
 #!/usr/bin/python2.6
-# Copyright (c) 2010 The Chromium OS Authors. All rights reserved.
+# Copyright (c) 2012 The Chromium OS Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
@@ -266,7 +266,7 @@
     # Turn off interactive delays
     os.environ["EBEEP_IGNORE"] = "1"
     os.environ["EPAUSE_IGNORE"] = "1"
-    os.environ["UNMERGE_DELAY"] = "0"
+    os.environ["CLEAN_DELAY"] = "0"
 
     # Parse the emerge options.
     action, opts, cmdline_packages = parse_opts(emerge_args, silent=True)