fix docs packstack.rst format error
fix docs packstack.rst format error

Change-Id: Ib36fe34d67af292568be159a95e2dd458d061673
Signed-off-by: Yuanbin.Chen <115798e15ddd872778e240322a1a46f7d51b5ce2@gmail.com>

fr34k8/packstack,mahak/packstack,fr34k8/packstack,stackforge/packstack,openstack/packstack,openstack/packstack,mahak/packstack,mahak/packstack,fr34k8/packstack,stackforge/packstack,openstack/packstack,stackforge/packstack