Add some comments to let user look up the latest
tag first, then execute command "git checkout <latest-tag>".
Update old kilo stable branch to the latest liberty stable
branch when you execute command "git clone -b ${BRANCH} ${REPO}
/opt/openstack-ansible".
Change-Id: I0597fbcc3950a99639174ab6398222fd3905caab
07a6cacd2a