metadata-agent should reuse auth_token across eventlet threads

[Akihiro Motoki]

Discussion from https://bugs.launchpad.net/quantum/+bug/1148017
The fix for Grizzly has been committed but there is a point to be improved in future. This bug is to trace it.

The current implementation of quantumclient does not support passing auth_token when keystone auth is used. Thus metadata-agent is forced to initiate a client per API call. It would be better to share auth_token across eventlet threads to reduce the overhead of keystone round trip.

To do this, the following action items are needed:
- Add a support of auth_token passing even when keystone auth is used in quantumclient. (https://bugs.launchpad.net/python-quantumclient/+bug/1152427)
- Update metadata-agent to used a new quantumclient.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/24646

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/24646
Committed: http://github.com/openstack/quantum/commit/49c1c981b5850c21ebcef5667a1198e79a8a3da4
Submitter: Jenkins
Branch: master

commit 49c1c981b5850c21ebcef5667a1198e79a8a3da4
Author: Oleg Bondarev <email address hidden>
Date: Mon Mar 18 19:36:27 2013 +0400

    Metadata agent: reuse authentication info across eventlet threads

    Fixes bug 1152429

    Change-Id: Ib65f08a46feb14abc97c0c83e57d076abd372a2c