Clean tempest dir before cloning.

This ensures that the code is recloned and if a venv is used, it is
unpacked into a clean clone. If a venv is unpacked multiple times (eg
multiple runs of the playbook) into the same dir then that venv may
become inconsistent.

This is a minimal fix for liberty as the full patch didn't backport
cleanly.

Bug: #1592509
Change-Id: I6f3c36a8150b83afabae8d397d5fc7340dbc93fd
Related-to: 13edcc092597b7109d0f75435ab4d07d56149998

playbooks/roles/os_tempest/tasks/tempest_install.yml

@@ -29,6 +29,15 @@
     - tempest-install
     - tempest-pip-packages
 
+# This ensures a clean clone, and that only one venv is ever unpacked
+# over the checkout. (previous problems were caused when multiple runs of this
+# playbook caused a venv to be expanded into a modifed clone which lead to an
+# inconsistent state)
+- name: Remove tempest git clone
+  file:
+    path: "{{ tempest_git_dest }}"
+    state: absent
+
 - name: Get tempest from git
   git:
     repo: "{{ tempest_git_repo }}"
@@ -47,6 +56,7 @@
   get_url:
     url: "{{ tempest_venv_download_url }}"
     dest: "/var/cache/{{ tempest_venv_download_url | basename }}"
+    force: yes
   ignore_errors: true
   register: get_venv
   tags: