Optimise pip install tasks

Unlike the Ansible apt module, the Ansible pip module does not
recognise a with_items list and process all the items at once.

To optimise the pip install tasks, this patch replaces the use
of with_items with a join filter so that the pip install task
does an install with all the packages in a list, ensuring that
the execution is one action instead of many.

Change-Id: Iee697a868e52bd5851864406e66fa3d58c7379a6

playbooks/utility-install.yml

@@ -73,14 +73,13 @@
         - utility-yum-packages
     - name: Install pip packages
       pip:
-        name: "{{ item }}"
+        name: "{{ utility_pip_packages | join(' ') }}"
         state: latest
         extra_args: "{{ pip_install_options|default('') }}"
       register: install_packages
       until: install_packages|success
       retries: 5
       delay: 2
-      with_items: "{{ utility_pip_packages }}"
       tags:
         - utility-pip-packages
     - name: Distribute private ssh key