test: apply Linux workaround to Linux only

Do not try Ubuntu/SUSE/Debian-specific hostnames for IPv6 localhost
unless we are on Linux.

Fixes: https://github.com/nodejs/node/issues/4546
PR-URL: https://github.com/nodejs/node/pull/5471
Reviewed-By: Evan Lucas <evanlucas@me.com>
Reviewed-By: Ben Noorhduis <info@bnoordhuis.nl>
Reviewed-By: Jeremiah Senkpiel <fishrock123@rocketmail.com>

test/common.js

@@ -80,7 +80,9 @@ var opensslCli = null;
 var inFreeBSDJail = null;
 var localhostIPv4 = null;
 
-exports.localIPv6Hosts = [
+exports.localIPv6Hosts = ['localhost'];
+if (process.platform === 'linux') {
+  exports.localIPv6Hosts = [
     // Debian/Ubuntu
     'ip6-localhost',
     'ip6-loopback',
@@ -91,7 +93,8 @@ exports.localIPv6Hosts = [
 
     // Typically universal
     'localhost',
-];
+  ];
+}
 
 Object.defineProperty(exports, 'inFreeBSDJail', {
   get: function() {