Ensure all the packages are installed

Instead of ensuring only the package failing was installed, we
here ensure all the usual packages are installed to the proper
version to avoid headaches in the future.

Change-Id: Ibf766551a4c17adf7763f8c986b0d39cd7148979

leap-upgrades/upgrade-utilities/pip-unify.yml

@@ -20,6 +20,10 @@
   vars:
     pip_upstream_url: "https://raw.githubusercontent.com/pypa/get-pip/430ba37776ae2ad89f794c7a43b90dc23bac334c/get-pip.py"
     pip_validate_certs: true
+    python_apt_packages:
+      - libssl-dev
+      - libffi-dev
+      - python-dev
   tasks:
     - name: "Copy global requirements"
       copy:
@@ -49,7 +53,9 @@
         dest: "/opt/get-pip.py"
         force: "yes"
         validate_certs: "{{ pip_validate_certs }}"
-      when: get_pip | failed
+      when:
+        - get_pip | failed
+        - pip_fallback_url is defined
       register: get_pip_fallback
       until: get_pip_fallback | success
       retries: 5
@@ -78,7 +84,7 @@
 
     - name: apt-get install libssl-dev
       apt:
-        name: libssl-dev
+        name: "{{ python_apt_packages }}"
         update_cache: yes
 
     - name: Re-install pip packaging requirements