Use policy_file parameter in quantum.policy

quantum.policy depends on configuration parameter `policy_file'
that is defined in quantum.common.context.

Tests from tests/unit/test_policy.py fail without this import.

Fixes: bug #1116263
Change-Id: Iba4792acb0fb6b34b4ebc99fec7bc729cdb306da
Cisco plugin cleanup follow up commit

A commit was made by Alex Xu (https://review.openstack.org/#/c/20073) a day before the Cisco plugin
cleanup that led to some deleted files creeping back into the Cisco plugin. This commit backs out
the deleted files again.

Blueprint cisco-plugin-cleanup

Change-Id: Ibad452dc0497dad452a33d6f41c1785231cd5d5b
Allow tools/install_venv_common.py to be run from within the source directory.

(Copy latest update from oslo)

Not doing this raised exceptions when it tried importing modules
that didn't exist in the path.

Fixes LP# 1116269

Change-Id: I3e2ed3ac96b51ec89def911054720d11bbcd9407
Merge "Allow tools/install_venv_common.py to be run from within the source directory."
Merge "Use policy_file parameter in quantum.policy"