Prefetch domains when connecting a storage server.

When a storage server is connected is searched for domains.
A uuid:findDomain method dictionary is saved for accelerate
further produces.

Related to BZ#891074

Change-Id: I8f2b19a566c659bac30a318d17cef929e0b2575b
Signed-off-by: Eduardo <ewarszaw@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/12869
Reviewed-by: Ayal Baron <abaron@redhat.com>
Tested-by: Ayal Baron <abaron@redhat.com>