FACTORY-980B: buildbot: disable vm tests on ZGB factory branch.

We don't need AU / performance tests for factory branches because only factory
installer and test images will be used - and factory will verify them.

This change may save more than 5000 seconds in factory image build time.

BUG=none, faster release request
TEST=none, next factory branch build will verify it.

Change-Id: Ib84ab28f37612ca72cf005caa1ecac872fed8265
Reviewed-on: http://gerrit.chromium.org/gerrit/8132
Reviewed-by: Hung-Te Lin <hungte@chromium.org>
Tested-by: Hung-Te Lin <hungte@chromium.org>
diff --git a/buildbot/cbuildbot_config.py b/buildbot/cbuildbot_config.py
index 59cf057..c3f3b94 100644
--- a/buildbot/cbuildbot_config.py
+++ b/buildbot/cbuildbot_config.py
@@ -663,6 +663,13 @@
 
 add_config('x86-zgb-release', [internal, full, official, release, {
   'board' : 'x86-zgb',
+  # For factory branch, we don't need those options.
+  'archive_build_debug' : False,
+  'chrome_tests' : False,
+  'quick_vm' : False,
+  'test_mod': False,
+  'upload_symbols': False,
+  'vm_tests' : False,
 }])
 
 add_config('x86-zgb_he-release', [internal, full, official, release, {