Want to implement `nut-scanner` support for multiple IP addresses resolving for one host name

[jimklimov]

A single start (or end) address, or even a CIDR address part, may be a host name. Until recently nut-scanner supported only one IP address range for queries; however since work on issue #2244 it became possible to schedule multiple ranges.

Currently the tool resolves a symbolic host name into a single IP address and scans it (or also its neighbors, in case of CIDR). For the case where multiple IP addresses resolve for one host name, we should generate several such ranges and walk them all.