Comment 10 for bug 1467120

Note: there is some discussion about modeling IP ranges as first-class citizens, so that we can support IPv6, and easily *un-reserving* a range. Without modeling ranges, to undo the command in (4) above would require num_addresses calls to the `release` API, which isn't good.

There is debate about whether or not this fits into 1.9, but it looks like we'll have to do it in order to do this the right way.

This may also help as we convert the concepts of dynamic and static ranges attached to a cluster interface to the more generic concept of DHCP-reserved ranges, and ranges reserved for some other reason.