Optimise pip install tasks
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: I1bd9d6f8e9ccd338e7417fa583d5a218ea499181

juledwar/openstack-ansible-os_ironic,juledwar/openstack-ansible-os_ironic