VMware: Enforce min vCenter server version 5.5

[OpenStack Infra]

https://review.openstack.org/440689
Dear bug triager. This bug was created since a commit was marked with DOCIMPACT.
Your project "openstack/cinder" is set up so that we directly report the documentation bugs against it. If this needs changing, the docimpact-group option needs to be added for the project. You can ask the OpenStack infra team (#openstack-infra on freenode) for help if you need to.

commit 549092a5483d1e6e5693b3cec79d3dca20905717
Author: Vipin Balachandran <email address hidden>
Date: Thu Mar 2 22:08:27 2017 +0530

    VMware: Enforce min vCenter server version 5.5

    Support for vCenter server 5.1 was deprecated in the Ocata
    release. Changing the minimum supported vCenter server version
    to 5.5. Also updating the version to reflect this change.

    DocImpact

    Change-Id: Ia33eccc088b76ca66be4d60ec32caa8f84076d2d