Merge pull request #1732 from edx/feanil/update_xml_tasks

Remove repos for courses we are about to checkout.

playbooks/roles/edxapp/tasks/xml.yml

+- name: remove all course data before checkout
+  file:
+    path="{{ edxapp_course_data_dir }}/{{ item.repo_name }}"
+    state=absent
+  with_items: EDXAPP_XML_COURSES
+
 - name: make the course data updatable by the edxapp user
   file:
     path="{{ edxapp_course_data_dir }}"