Adding/Removing/Updateing/Deleteing a server should update existing zones

[Kiall Mac Innes]

Currently, when you add/remove/update/delete a server, existing domains do not get updated to match.

We should implement create/update/delete_server methods in the backends, and have central call them when necessary.

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/45078
Committed: http://github.com/stackforge/designate/commit/f2c8658b944ca75832e9e1e02fa2caec5e568231
Submitter: Jenkins
Branch: master

commit f2c8658b944ca75832e9e1e02fa2caec5e568231
Author: emmanuel.ankutse <email address hidden>
Date: Wed Sep 4 08:24:52 2013 -0500

    Update domains when servers are created, modified or deleted

    Existing domains do not get updated in the backend when new servers are
    added or existing ones modified or deleted.
    This is rectified in this fix by implementing methods in all of the backends.
    Three abstract methods were added to the base module that all backends
    inherit from and implemented in all backends.
    The three methods implemented are create_server, update_server, and
    delete_server.
    The methods are called from central/service.py as needed.

    Change-Id: I1ac9add27f91ee6d73fdcfda5b2ef8c0c1ecb0ab
    Closes-Bug: #1214869