fix(api): callback called twice

Revert the change to add the callback if it is undefined.

Fixes #343

Author: wzrdtales

api.js

@@ -680,8 +680,6 @@ function _assert(err, callback) {
 
 function executeUp(internals, config, callback) {
 
-  var callback = callback || internals.onComplete;
-
   if (!internals.argv.count) {
     internals.argv.count = Number.MAX_VALUE;
   }
@@ -711,8 +709,6 @@ function executeUp(internals, config, callback) {
 
 function executeDown(internals, config, callback) {
 
-  var callback = callback || internals.onComplete;
-
   if (!internals.argv.count) {
     log.info('Defaulting to running 1 down migration.');
     internals.argv.count = 1;
@@ -736,8 +732,6 @@ function executeDown(internals, config, callback) {
 
 function executeDB(internals, config, callback) {
 
-  var callback = callback || internals.onComplete;
-
   if (internals.argv._.length > 0) {
     internals.argv.dbname = internals.argv._.shift().toString();
   } else {
@@ -787,8 +781,6 @@ function executeDB(internals, config, callback) {
 
 function executeSeed(internals, config, callback) {
 
-  var callback = callback || internals.onComplete;
-
   if (internals.argv._.length > 0) {
     internals.argv.destination = internals.argv._.shift().toString();
   }
@@ -820,8 +812,6 @@ function executeSeed(internals, config, callback) {
 
 function executeUndoSeed(internals, config, callback) {
 
-  var callback = callback || internals.onComplete;
-
   if (!internals.argv.count) {
     log.info('Defaulting to running 1 down seed.');
     internals.argv.count = 1;