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>
1 file changed