As of Ocata, the minimum version of VMware vCenter will be
enforced at 5.1.0. And any version less than 5.5.0 will be
warned as deprecated. In two releases, 5.5.0 will become the
new minimum version.
The VMware driver CI will has already migrated to vCenter 6.0.
DocImpact: Need version updates on the minimum vCenter included in
http://docs.openstack.org/mitaka/config-reference/compute/hypervisor-vmware.html
Change-Id: I9f13e6cd6a49699f2b3cdce892fbf02634bf7618