Ensure get-pip.py is retrieved properly

Without force: "yes" the get_url module will only retrieve the file if
the destination doesn't exist. This causes issues if, for example, the
get-pip.py exists but is empty (due to an issue), or if the get-pip.py
is updated at some point.

Change-Id: I9d6933c837e0e38d51dfb57a3eddd1ca461e0723
Closes-Bug: #1429165

playbooks/roles/pip_install/tasks/main.yml

@@ -42,6 +42,7 @@
   get_url:
     url: "{{ pip_get_pip_url }}"
     dest: "/opt/get-pip.py"
+    force: "yes"
     validate_certs: "no"
   register: get_pip
   until: get_pip|success