dns: refactor internal/dns/promises.js

Use `isIP()` instead of `isIPv4()` since it does the additional
functionality that we were adding after our calls to `isIP()`.

This not-so-incidentally also increases code coverage from tests. At
least one of the replaced ternaries was difficult to cover reliably
because operating system/configuration variances were too unpredictable.

lib/internal/dns/promises.js

@@ -7,7 +7,7 @@ const {
 } = require('internal/dns/utils');
 const { codes, dnsException } = require('internal/errors');
 const { toASCII } = require('internal/idna');
-const { isIP, isIPv4, isLegalPort } = require('internal/net');
+const { isIP, isLegalPort } = require('internal/net');
 const {
   getaddrinfo,
   getnameinfo,
@@ -31,7 +31,7 @@ function onlookup(err, addresses) {
     return;
   }
 
-  const family = this.family ? this.family : isIPv4(addresses[0]) ? 4 : 6;
+  const family = this.family ? this.family : isIP(addresses[0]);
   this.resolve({ address: addresses[0], family });
 }
 
@@ -48,7 +48,7 @@ function onlookupall(err, addresses) {
 
     addresses[i] = {
       address,
-      family: family ? family : isIPv4(addresses[i]) ? 4 : 6
+      family: family ? family : isIP(addresses[i])
     };
   }