fix(multiple-receivers): register callback when attaching

Bug missed in the promisification of createReceiver where callbacks
passed in with createReceiver during attachment were not retained.

lib/amqp_client.js

@@ -440,6 +440,8 @@ AMQPClient.prototype.createReceiver = function(source, filter, cb) {
 
   var linkName = source + '_RX';
   if (this._attaching[linkName]) {
+    self._onReceipt[linkName].push(cb);
+
     return new Promise(function(resolve, reject) {
       var attachingListener = function(link) {
         if (link.name === linkName) {

test/integration/qpid/client.test.js

@@ -1,6 +1,7 @@
 'use strict';
 var AMQPClient = require('../../..').Client,
     Message = require('../../../lib/types/message'),
+    Promise = require('bluebird'),
     config = require('./config'),
     expect = require('chai').expect;
 
@@ -36,6 +37,29 @@ describe('Client', function() {
       });
   });
 
+  it('should be able to create multiple receivers for same link', function(done) {
+    var receviedCount = 0;
+    var messageHandler = function(err, message) {
+      expect(message.body).to.equal('TESTMESSAGE');
+      receviedCount++;
+      if (receviedCount === 2) done();
+    };
+
+    test.client.connect(config.address)
+      .then(function() {
+        return Promise.all([
+          test.client.createReceiver(config.defaultLink, null, messageHandler),
+          test.client.createReceiver(config.defaultLink, null, messageHandler)
+        ]);
+      })
+      .then(function() {
+        return test.client.send('TESTMESSAGE', config.defaultLink);
+      })
+      .catch(function(err) {
+        expect(err).to.not.exist;
+      });
+  });
+
   describe('Messages', function() {
     [
       {