Add show resource support for designate resources

[Kanagaraj Manickam]

designate client does not provide the support for to_dict() to the client entity objects. This bug is filed to add _show_resource () to the designate resources, so that, it will be able to report the resource dict.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/213677

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/213677
Committed: https://git.openstack.org/cgit/openstack/heat/commit/?id=f388ca270f45a885271bd21832f5d929340b02e8
Submitter: Jenkins
Branch: master

commit f388ca270f45a885271bd21832f5d929340b02e8
Author: Kanagaraj Manickam <email address hidden>
Date: Mon Aug 17 16:03:13 2015 +0530

    Adds _show_resource support to designate plugins

    Adds the _show_resource() to designate plugins Domain
    and Record.

    Change-Id: If75457ee45b505ed7ce5e853b0f270cff71dc674
    Closes-bug: #1484867