Add callback to client#end (#1106)

A long standing bug was the pure JS client didn't accept or call a callback on `client.end`.  This is inconsistent with both the documentation & general node patterns.

This fixes the issue & adds a test.  The issue did not exist in the native version of the client.

lib/client.js

@@ -336,8 +336,11 @@ Client.prototype.query = function(config, values, callback) {
   return query;
 };
 
-Client.prototype.end = function() {
+Client.prototype.end = function(cb) {
   this.connection.end();
+  if (cb) {
+    this.connection.once('end', cb);
+  }
 };
 
 Client.md5 = function(string) {

lib/connection.js

@@ -122,6 +122,9 @@ Connection.prototype.attachListeners = function(stream) {
       packet = self._reader.read();
     }
   });
+  stream.on('end', function() {
+    self.emit('end');
+  });
 };
 
 Connection.prototype.requestSsl = function() {

test/integration/client/end-callback-tests.js

@@ -0,0 +1,6 @@
+var helper = require('./test-helper')
+
+var client = helper.client(assert.success(function() {
+  client.end(assert.success(function() {
+  }))
+}))

test/integration/test-helper.js

@@ -7,9 +7,9 @@ if(helper.args.native) {
 }
 
 //creates a client from cli parameters
-helper.client = function() {
+helper.client = function(cb) {
   var client = new Client(helper.config);
-  client.connect();
+  client.connect(cb);
   return client;
 };