As of Ansible v2.2 all the missing modules bifrost requires are included
in the pip-installable Ansible package.
Let's allow then for a possiibility for bifrost to install Ansible
directly from PyPI (into the system or in virtualenv) instead
of from cloned source repo.
This patsh first extracts the installation of binary/Python dependencies
and installation of Ansible itself from the "env-setup.sh" script to two
separate scripts "install-deps.sh" and "install-ansible-source.sh".
It also adds a third script "install-ansible-pip.sh" that is called when
environment variable ANSIBLE_FROM_PYPI is set to "True"
(default is "False" for backward compatibility).
It then looks up ANSIBLE_PIP_VERSION env variable (defaults to "2.2")
and pip-installs Ansible of that given version strictly.
Change-Id: Ia72e06d7bf127569d423fa521b8ddab87453809e
