Fix duplicate check for "only allow internal addresses if we are on a network with nonstandard authorities"
We have this code in config.c:
```
if (tor_addr_is_internal(&myaddr, 0)) {
/* make sure we're ok with publishing an internal IP */
if (!options->DirAuthorities && !options->AlternateDirAuthority) {
/* if they are using the default authorities, disallow internal IPs
* always. */
log_fn(warn_severity, LD_CONFIG,
"Address '%s' resolves to private IP address '%s'. "
"Tor servers that use the default DirAuthorities must have "
"public IP addresses.", hostname, addr_string);
tor_free(addr_string);
return -1;
}
...
```
And we now have this code in router.c (since legacy/trac#17153):
```
/* Like IPv4, if the relay is configured using the default
* authorities, disallow internal IPs. Otherwise, allow them. */
const int default_auth = (!options->DirAuthorities &&
!options->AlternateDirAuthority);
if (! tor_addr_is_internal(&p->addr, 0) || ! default_auth) {
ipv6_orport = p;
break;
...
```
These two checks are similar and I'd prefer that they be merged when possible.
issue