Detangle the use of a Red Hat OS family as requiring openvswitch

The current Salt script hard-coded the use of openvswitch when installing on a Red Hat OS family.

This PR makes the use of openvswitch an explicit setting in the grains.conf file so it can be used by the Vagrant-based cluster for local development, but ignored when using a Red Hat based OS on an alternate cloud provider.

Closes #1152 
need to check if this grain is defined before checking value.