Go 1.20 introduced DNS/CNAME handling changes. This can cause an
IP address represented in hex, oct, etc to be looked up as DNS and
fail. This change introduces a mock DNS resolver.

Note, with the mock resolver, we don't need to use 0x7f000001 any
longer. Keeping because it was already there.

Signed-off-by: Matt Farina <matt.farina@suse.com>