Remove query emit 'end' event when query has error

Closes #547

lib/query.js

@@ -93,11 +93,9 @@ Query.prototype.handleError = function(err, connection) {
   //if callback supplied do not emit error event as uncaught error
   //events will bubble up to node process
   if(this.callback) {
-    this.callback(err);
-  } else {
-    this.emit('error', err);
+    return this.callback(err);
   }
-  this.emit('end');
+  this.emit('error', err);
 };
 
 Query.prototype.submit = function(connection) {

test/integration/client/query-error-handling-tests.js

@@ -12,10 +12,16 @@ test('error during query execution', function() {
         pidColName = 'pid';
         queryColName = 'query';
       }
-      client.query(sleepQuery, assert.calls(function(err, result) {
+      var query1 = client.query(sleepQuery, assert.calls(function(err, result) {
         assert(err);
         client.end();
       }));
+      //ensure query1 does not emit an 'end' event
+      //because it was killed and received an error
+      //https://github.com/brianc/node-postgres/issues/547
+      query1.on('end', function() {
+        assert.fail('Client with an error should not emit "end" event')
+      })
       var client2 = new Client(helper.args);
       client2.connect(assert.success(function() {
         var killIdleQuery = "SELECT " + pidColName + ", (SELECT pg_terminate_backend(" + pidColName + ")) AS killed FROM pg_stat_activity WHERE " + queryColName + " = $1";