Add manageable server information into metadata

[wanghao]

Now when Mogan manage the baremetal node from driver, Mogan didn't know it is a managed server. We need add this information to server's metadata for internal use.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/515585

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/515585
Committed: https://git.openstack.org/cgit/openstack/mogan/commit/?id=bdbf3f81e718168465f37f40d121f1e139b317e4
Submitter: Zuul
Branch: master

commit bdbf3f81e718168465f37f40d121f1e139b317e4
Author: wanghao <email address hidden>
Date: Fri Oct 27 12:35:27 2017 +0800

    Add manageable server information into system metadata

    Now when Mogan manage the baremetal node from driver,
    Mogan didn't know it is a managed server.
    We need add this information "managed_server=True" to
    system metadata for internal use.

    So this patch will finish two jobs:
    1. Implements the system metadata in Mogan
    2. Add manageable server information into system metadata

    Co-Authored-By: Xinran WANG <email address hidden>
    Change-Id: I89947796e120d89ec56f8f5daeb9774cf15b6bd0
    Implements: blueprint system-metadata
    Closes-Bug: #1727913