Add support for python3.8 get-pip.py on focal

We already have old support for older python3.6 and bionic via this
method. Now that get-pip.py doesn't support python3.8 we do the same
thing for focal. It is unfortunate that they can't keep the script
broadly compatible but we already seem to have tooling to handle this so
take advantage of it.

Change-Id: Iba0838bc0757112905f7f1d5edfe1d3b395e470e

playbooks/roles/pip3/tasks/focal.yaml

@@ -0,0 +1,6 @@
+# Latest pip (and get-pip.py) does not support the Python 3.8 on Ubuntu Focal
+- name: Download get-pip.py
+  command: wget https://bootstrap.pypa.io/pip/3.8/get-pip.py
+  args:
+    chdir: /var/lib
+    creates: /var/lib/get-pip.py