Add documentation for setting vif_type on vSphere CPI
Add documentation for setting vif_type on vSphere CPI

[#149338519](https://www.pivotaltracker.com/story/show/149338519)

Signed-off-by: Neha Jain <b21d539db42de6b5c6c25a59f239550a20ac2588@vmware.com>

cloudfoundry/docs-bosh