Moving backend from system calls to openstack/ovsdbapp

[rmackinnon]

Was reviewing the backend code and saw most of the control/commands were executing as subprocess calls. I'm super interested in your project (for my own selfish reason, aka: 'I'm looking at running OVN/OVS and there doesn't seem to be anything that I can use to manage things, outside of this project'). I'm interested in putting in some work for the backend of this project (as I do mostly python Flask and utility work), this is right up my ally.

Maybe we move calls to unix socket calls with Openstack's ovsdbapp python module? Would greatly improve performance. I can get cracking at a PR if this is something of interest.