Fix magnum-template-manage

[OpenStack Infra]

https://review.openstack.org/385756
Dear bug triager. This bug was created since a commit was marked with DOCIMPACT.
Your project "openstack/magnum" is set up so that we directly report the documentation bugs against it. If this needs changing, the docimpact-group option needs to be added for the project. You can ask the OpenStack infra team (#openstack-infra on freenode) for help if you need to.

commit af59ea68b8e4998f54caeb864a2bb6dc9ddb03c7
Author: yatin <email address hidden>
Date: Thu Oct 13 10:42:36 2016 +0530

    Fix magnum-template-manage

    After patch: https://review.openstack.org/#/c/374906/
    magnum-template-manage didn't worked because load_entry_point
    method moved to Driver class.
    With this patch, magnum-template-manage can be used to list
    all available drivers in magnum.

    The patch also renames magnum-template-manage cli to
    magnum-driver-manage.
    Drivers can now be listed using:-
    magnum-driver-manage list-drivers
    magnum-driver-manage list-drivers -d -p

    DocImpact

    Change-Id: I17ba94b0e2000486b5fcbf792991ad98183bd26c
    Partially-Implements: blueprint bay-drivers
    Closes-Bug: #1632630