Previously the path to the openshift-ansible's prerequisites playbook
was hardcoded to
/usr/share/ansible/openshift-ansible/playbooks/prerequisites.yml. This
commit introduces the `OpenShiftPrerequisitesPlaybook` heat parameter
to make it configurable.
Also add more explicit description for the other playbook path
parameters and update the default path for OpenShiftUpgradePlaybook
that was broken since the move to openshift-ansible 3.10.
Change-Id: I2260cb8b0cef9650c707d4db917a3281a697912d
46246e8745