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

scripts/get-ansible-role-requirements.yml

@@ -17,6 +17,7 @@
   hosts: localhost
   connection: local
   user: root
+  gather_facts: false
   tasks:
     - name: Remove target directory if required
       file:
@@ -135,6 +136,6 @@
     role_file: "{{ playbook_dir }}/../ansible-role-requirements.yml"
     role_path_default: '/etc/ansible/roles'
     user_roles: "{{ lookup('file', user_role_path, errors='ignore')|default([], true) | from_yaml }}"
-    user_role_path: "{{ lookup('env', 'OSA_CONFIG_DIR')|default('/etc/openstack_deploy') ~ '/' ~ user_role_file }}"
+    user_role_path: "{{ lookup('env', 'OSA_CONFIG_DIR')|default('/etc/openstack_deploy') ~ '/' ~ (user_role_file|default('')) }}"
     git_clone_retries: 2
     git_clone_retry_delay: 5