Help the static analyzer in `handle_ice`

Help the static analyzer in `handle_ice`

Clang's static analyzer thinks we could be using `hosts` here when it
is NULL.  We probably weren't, but it's easy to see how it could think
so.  We were checking whether `from_addr` matched `ice->addr` three
times, and between the second on third time we might have modified the
`ice->addr`; however we only get there if it matched the second time,
so we could only make it not match at that point and avoid the third
branch.  We can't make it match where it did not before.

We'll simplify the logic a bit here so static analyzers (and humans)
can hopefully see this more readily.