ICC always uses IPv4 callbacks in a dualstack environment

Description of problem:

Currently, CBO provides ICC with full URLs for Ironic and Inspector, which use whatever the default network family is. If a host is V6-only, it won't successfully deploy on a dualstack cluster where V4 is the primary network.

It's not trivial to fix. For the virtual media URL, we make BMO check the BMC address family and decide which URL to provide. This may work (although not 100% guaranteed) for callback URLs as well, but the logic has to live in ICC.