LABEL should replace MAINTAINER (deprecated) in Dockerfile.j2

[Mike Chen]

According to Docker's official guide, the LABEL instruction is much more flexible and recommended to replace the MAINTAINER (deprecated) instruction in a Dockerfile. So we should follow the suggestion and update the line of concern in Dockerfile.j2.

Links:
https://docs.docker.com/engine/reference/builder/#maintainer-deprecated
https://github.com/openstack/kolla/blob/master/docker/base/Dockerfile.j2#L2

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/457513

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/457513
Committed: https://git.openstack.org/cgit/openstack/kolla/commit/?id=8c463a47a9c988df70046f7d343af0441bf29f4d
Submitter: Jenkins
Branch: master

commit 8c463a47a9c988df70046f7d343af0441bf29f4d
Author: Chen <email address hidden>
Date: Tue Apr 18 17:20:03 2017 +0900

    Use LABEL instead of MAINTAINER (deprecated) in all Dockerfile.j2

    Use LABEL instruction instead of MAINTAINER (deprecated) instruc-
    tion as suggested by Docker's official dockerfile guide.
    docs.docker.com/engine/reference/builder/#maintainer-deprecated

    Closes-Bug: #1683652

    Change-Id: Ie87a1ddf31aefcd0b623fd2837d78de420e76898

[OpenStack Infra (hudson-openstack)]

This issue was fixed in the openstack/kolla 5.0.0.0b2 development milestone.