Implements blueprint os-api-network-create
The ability to create new networks is currently only exposed by the
nova-manage CLI. Here we add support for network creation in the
os-networks API extension.
With the exception of num_networks and network_size, all the parameters
supported by 'nova-manage network create' are supported. Only a single
network may be created by each API call.
To avoid code duplication, the nova-manage code is refactored and moved
into NetworkManager so that it can be re-used by the API.
DocImpact
Change-Id: I682d498ab35ea43b553b64e13e677fe9eeb8e08b
7b78a0d13d