Add Fedora based docker file creation
Add Fedora based docker file creation

This docker image is using Python 3.6 as default instead of the 2.6
version used by the default image.
In order to create the Fedora docker image, use the following command:
docker build -t dragonflow -f Dockerfile.fedora .

Recently we have added features that are supported only with Python 3,
so this docker will allow us to run them natively.
e.g. https://review.openstack.org/#/c/616106

Co-Authored-By: Omer Anson <9dd9a1208ec9752dc499531fdd9da421f3973e9b@toganetworks.com>
Change-Id: Iefd88738424906e832564b23f69320b775c98376
Partially-Implements: blueprint add-dragonflow-api

openstack/dragonflow,openstack/dragonflow,openstack/dragonflow