Add suport for the Publish over SSH plugin.

Change-Id: Id06bd57c1d290df98c05b3cb19066013635199a3
Reviewed-on: https://review.openstack.org/26831
Reviewed-by: James E. Blair <corvus@inaugust.com>
Approved: Jeremy Stanley <fungi@yuggoth.org>
Reviewed-by: Jeremy Stanley <fungi@yuggoth.org>
Tested-by: Jenkins