Add support for 3.5 DCs/Clusters

This patch allows Clusters and DCs running version 3.4 to use FakeVDSM.
It still has some limitations, but common flows now work.

Change-Id: I5dfff0ea356f289d6be2fae940925b64617e196e
Signed-off-by: lzelkha@redhat.com <lzelkha@redhat.com>