Add and Delete Contrail Nodes/Roles using Ansible

Add contrail-ansible-deployer playbooks and workflows to give user the ability to modify a Contrail Cluster.

Ways to modify:
Add a role or a set of roles on an existing node
Delete a role or a set of roles on an existing node
Add roles to a node not currently deployed
Delete all roles from a node and remove node from cluster

For Release R5.1, we will be supporting only add/delete of compute nodes