Use a random TCP port for testing timeouts/rejects

This fixes a test failure when the host has something listening
on the LDAP TCP port. Previously, the test cases would assume
that the port was free and they would not connect.

For #612

package.json

@@ -27,6 +27,7 @@
     "verror": "^1.8.1"
   },
   "devDependencies": {
+    "get-port": "^5.1.1",
     "husky": "^3.0.4",
     "snazzy": "^8.0.0",
     "standard": "^14.0.2",

test/client.test.js

@@ -5,6 +5,7 @@ const assert = require('assert')
 const tap = require('tap')
 const uuid = require('uuid')
 const vasync = require('vasync')
+const getPort = require('get-port')
 const { getSock } = require('./utils')
 const ldap = require('../lib')
 const { Attribute, Change } = ldap
@@ -1495,8 +1496,9 @@ tap.test('resultError handling', function (t) {
 })
 
 tap.test('connection refused', function (t) {
+  getPort().then(function (unusedPortNumber) {
     const client = ldap.createClient({
-    url: 'ldap://0.0.0.0'
+      url: `ldap://0.0.0.0:${unusedPortNumber}`
     })
 
     client.bind('cn=root', 'secret', function (err, res) {
@@ -1507,10 +1509,12 @@ tap.test('connection refused', function (t) {
       t.end()
     })
   })
+})
 
 tap.test('connection timeout', function (t) {
+  getPort().then(function (unusedPortNumber) {
     const client = ldap.createClient({
-    url: 'ldap://example.org',
+      url: `ldap://example.org:${unusedPortNumber}`,
       connectTimeout: 1,
       timeout: 1
     })
@@ -1532,3 +1536,4 @@ tap.test('connection timeout', function (t) {
       t.end()
     })
   })
+})