remove accidental use of node crypto

lib/acme.js

@@ -988,9 +988,14 @@ ACME._getCertificate = function(me, options) {
 		// a little bit of random to ensure that getZones()
 		// actually returns the zones and not the hosts as zones
 		var dnsHosts = options.domains.map(function(d) {
-			var rnd = require('crypto')
-				.randomBytes(2)
-				.toString('hex');
+			var rnd = parseInt(
+				Math.random()
+					.toString()
+					.slice(2),
+				10
+			)
+				.toString(16)
+				.slice(0, 4);
 			return rnd + '.' + d;
 		});
 		promiseZones = ACME._getZones(