docker plugin add read_only properties

[LiangChen]

Docker 1.5 and docker-py both support the read_only capability.
By using this capability in combination with volumes, you can make sure containers only persist data where it can be managed in a known location.
For the security, I think we should support it in the heat-docker.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/166122

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/166122
Committed: https://git.openstack.org/cgit/openstack/heat/commit/?id=3944fe1c7ff55f8426184a15511ec8e772de4caa
Submitter: Jenkins
Branch: master

commit 3944fe1c7ff55f8426184a15511ec8e772de4caa
Author: LiangChen <email address hidden>
Date: Fri Mar 20 15:00:45 2015 +0800

    Docker plugin add read_only property

    Docker 1.5 and docker-py 1.0.0 support the read_only parameter when
    starting containers(docker run --read-only).

    By using this capability in combination with volumes, you can make sure
    containers only persist data where it can be managed in a known location.

    we should support it in the heat-docker

    Change-Id: I6fdc3e46bb86b387a187f8fceb22997daed0a9f1
    Closes-bug: #1430211