virtualenv not using system packages

[Sam Yaple]

The virutalenv should use the system site-packages if the python libs are not available in the virtualenv

This is especially important when talking about the ceph-libs. We install the package provided ceph libs to ensure they work properly with the ceph cluster installed. This was attempted in the bug linked below, but unfortunately that also duplicates the install of glance.

Related-Bug: #1524684

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/261784

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/261784
Committed: https://git.openstack.org/cgit/openstack/kolla/commit/?id=cda0459ad1c6c51ec5de3bd4492c96e1db48c4d7
Submitter: Jenkins
Branch: master

commit cda0459ad1c6c51ec5de3bd4492c96e1db48c4d7
Author: SamYaple <email address hidden>
Date: Sun Dec 27 02:41:30 2015 +0000

    Fix pip install settings

    There were some inconsistencies with pip install instructions
    thoughout Kolla. We fix those here.

    Additionally, we fix the virtualenv to properly use the site-packages
    on the host if a library is not available in the venv.

    Change-Id: Ib84d48e8826bb96060338b3fa0782620c98794a8
    Related-Bug: #1524684
    Closes-Bug: #1529434