Adds vnc_enabled=True and novncproxy_base_url

Bug 1246192 is a duplicate of 1246194

Change-Id: Ic37fb8c17a9b2632e11502eff334fb75c1e468f0
Closes-bug: 1246194
backport: havana
(cherry picked from commit 0b04c7af979c28f145ada96cdd0e435d448b4c1f)