sorry but i have te same problem with provider network for physical network i edited de ml2 conf but when i create a new network :

openstack network create  --share --external \
  --provider-physical-network provider \
  --provider-network-type flat provider

I still have this error :

openstack network create  --share --external \
  --provider-physical-network provider \
  --provider-network-type flat provider
Error while executing command: BadRequestException: 400, Invalid input for operation: physical_network 'provider' unknown for flat provider network.