core: VdsDAO.getAllWithName now returns instance

List<VDS> VdsDAO.getAllWithName(String) has been changed to
VDS VdsDAO.getByName(String) because VDS name is unique

Change-Id: I1a0cb37c98f1a4373028e6210e45261cd432eed3
Bug-Url: https://bugzilla.redhat.com/894382
Signed-off-by: Martin Perina <mperina@redhat.com>