webadmin: Remove unneccessary queries from Cluster Dialog show

When the cluster dialog box is opened, it queries the list of Vds
and Vms. However, this info is already found in the UI, added in a
previous patch http://gerrit.ovirt.org/#/c/26980/

This patch removes the unneeded DB calls

Change-Id: I619bb4971e87e7521653469b7c4a9208ca893d0e
Bug-Url: https://bugzilla.redhat.com/1139688
Signed-off-by: lzelkha@redhat.com <lzelkha@redhat.com>