"invalid RPZ prefix length" log message improperly displays the prefix labels, not length

Summary

Jinmei reports a likely regression in 9.11.3-S1:

9.11.3-S1 now shows logs like this:

11-May-2018 14:42:12.059 invalid rpz IP address "33.1.2.0.192.rpz-ip.rpz"; invalid IPv4 prefix length of 33.1.2.0.192

Previously (e.g., 9.10.3-P4) it was:

11-May-2018 14:45:00.471 invalid rpz IP address "33.1.2.0.192.rpz-ip.rpz"; invalid IPv4 prefix length of 33

Besides the fact that the new format breaks backward compatibility, I find the new format more confusing than improvement. So I suspect it's more likely to be a regression than an intentional change.

Code-wise the reason for the change is the removal of the first line from the following in lib/dns/rpz.c:name2ipkey():

*cp2 = '\0';
if (prefix_num < 1U || prefix_num > 128U) {
   badname(log_level, src_name, "; invalid prefix length of ", prefix_str);
   return (ISC_R_FAILURE);
}