fold sysinfo into network

the backends are network backends

src/dns/namecheap.js

@@ -16,9 +16,9 @@ const assert = require('assert'),
     debug = require('debug')('box:dns/namecheap'),
     dig = require('../dig.js'),
     dns = require('../dns.js'),
+    network = require('../network.js'),
     safe = require('safetydance'),
     superagent = require('superagent'),
-    sysinfo = require('../sysinfo.js'),
     util = require('util'),
     waitForDns = require('./waitfordns.js'),
     xml2js = require('xml2js');
@@ -37,7 +37,7 @@ function injectPrivateFields(newConfig, currentConfig) {
 async function getQuery(domainConfig) {
     assert.strictEqual(typeof domainConfig, 'object');
 
-    const ip = await sysinfo.getServerIPv4(); // only supports ipv4
+    const ip = await network.getIPv4(); // only supports ipv4
 
     return {
         ApiUser: domainConfig.username,