Add default value for user_role_file when cloning git repos
Add default value for user_role_file when cloning git repos

This change allows scripts/get-ansible-role-requirements.yml playbook
to be used as a standalone tool for cloning all OSA repos
referenced in ansible-role-requirements.yml into a user defined workspace.
This is useful for automatically bootstrapping a development environment
with all of the OSA ansible roles cloned outside /etc/ansible/roles.

Example:

ansible-playbook scripts/get-ansible-role-requirements.yml -e role_path_default=/path/to/workspace

Change-Id: I207853206435f0ec5faca95c69c25230e0c6b50c

stackforge/os-ansible-deployment,openstack/openstack-ansible,stackforge/os-ansible-deployment,openstack/openstack-ansible