contrail-charms: support interface name as control-network parameter

[Bernhard Koessler]

currently, the contrail-charms for contrail-controller, contrail-analytics and contrail-analyticsdb expect a CIDR as input to the control-network paramter. This is impractical in deployments where dynamic subnets per rack are deployed which are not known at the time of bundle generation. In those cases it would be better to be able to define an interface name in line with vrouter interface configuration in contrail-agent charm.

My hack I used to achieve this is as follows:

contrail-[controller|analytics|analyticsdb]/hooks/common_utils.py:

def get_ip():
    network = config.get("control-network")
    ip = None
    try:
      ip = get_address_in_network(network) if network else None
    except ValueError:
      log("control-network not defined as CIDR")
    if not ip:
      # if no CIDR format is provided, treat as interface name
      ip = get_iface_addr(iface=network)[0] if network else None
    if not ip:
        ip = _get_default_ip()
    return ip