Lack of mistral/murano client packages in rally docker image

[Lingxian Kong]

In the Dockerfile of Rally, the packages in the optional-requirements.txt are not installed, so rally user can not do benchmarking of Mistral, Murano, etc.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/176794

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/176794
Committed: https://git.openstack.org/cgit/openstack/rally/commit/?id=e5855ecb364465e69ec2e7c29647d7c7fd071b22
Submitter: Jenkins
Branch: master

commit e5855ecb364465e69ec2e7c29647d7c7fd071b22
Author: LingxianKong <email address hidden>
Date: Thu Apr 23 22:53:15 2015 +0800

    Install optional-requirement packages for Rally docker image

    Ensure python-mistralclient, python-muranoclient or other packages
    are included in the Rally docker image, so user could do benchmarking
    without extra work.

    Change-Id: I246a961d02308aee87a77098bdd631cf1a3bbd0c
    Closes-Bug: #1447648