install_venv_common.py fails wihout oslo-cfg on host

[Isaku Yamahata]

install_venv_common.py requires oslo-config on hosts.
The causing change set is of Change-Id: I4815aeb8a9341a31a250e920157f15ee15cfc5bc
commit cfda6bc4fb4307fce51e9ec2e049242737dc9c33

I think this isn't intentional and install_venv_common should be independent on oslo-config

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/22509

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/22509
Committed: http://github.com/openstack/quantum/commit/8501e9d48dd29e0b0ddc5e5297365922e4946171
Submitter: Jenkins
Branch: master

commit 8501e9d48dd29e0b0ddc5e5297365922e4946171
Author: Isaku Yamahata <email address hidden>
Date: Thu Feb 21 11:57:59 2013 +0900

    Sync latest install_venv_common.py with olso

    This patch syncs with oslo change set of
    > c78b2ab Avoid using cfg in install_venv_common

    So that oslo-config isn't needed to run install_venv

    Change-Id: Ia7ee923a53e09c0c6a525294ec4a5dc9d31c3bed
    Fixes: bug #1131009
    Signed-off-by: Isaku Yamahata <email address hidden>