fix(refresh): it has to clear all tables if no language key is specified

The `$translate.refresh()` method has to clear all tables if no language key is specified.
In other case it may cause inconsistent state of different translation tables inside the module.

Fixes the following case:
// The 'A' language is not a fallback language
* $translate.use('A');
* $translate.use('B');
* $translate.refresh(); // only 'B' language is refreshed
* $translate.use('A'); // old translation table is used instead of fetching a new one

Related to #988.

src/service/translate.js

@@ -1714,10 +1714,8 @@ function $translate($STORAGE_KEY, $windowProvider) {
           }
 
           var allTranslationsLoaded = function (tableData) {
+            $translationTable = {};
             angular.forEach(tableData, function (data) {
-              if ($translationTable[data.key]) {
-                delete $translationTable[data.key];
-              }
               translations(data.key, data.table);
             });
             if ($uses) {

test/unit/service/translate.spec.js

@@ -1522,6 +1522,7 @@ describe('pascalprecht.translate', function () {
 
       beforeEach(module('pascalprecht.translate', function ($translateProvider, $provide) {
         $translateProvider
+          .translations('de_DE', translationMock)
           .translations('en_EN', translationMock)
           .preferredLanguage('en_EN')
           .useLoader('customLoader');
@@ -1579,6 +1580,40 @@ describe('pascalprecht.translate', function () {
         expect(newValue).toEqual('bar');
       });
 
+      it('should clear completelly inactive translation tables', function () {
+        var value;
+
+        function setValue(answer) {
+          value = answer;
+        }
+
+        function fetchTranslation() {
+          $translate('EXISTING_TRANSLATION_ID').then(setValue, setValue);
+          $rootScope.$digest();
+        }
+
+        function changeLanguage(lang) {
+          $translate.use(lang);
+          $rootScope.$digest();
+        }
+
+        changeLanguage('de_DE');
+        fetchTranslation();
+        expect(value).toEqual('foo'); // found
+
+        changeLanguage('en_EN');
+        $translate.refresh();
+        $timeout.flush();
+        $rootScope.$digest();
+
+        changeLanguage('de_DE');
+        $timeout.flush(); // Expect the `de_DE` language to be loaded
+        $rootScope.$digest();
+
+        fetchTranslation();
+        expect(value).toEqual('EXISTING_TRANSLATION_ID'); // not found
+      });
+
       it('should emit $translateRefreshStart event', function () {
         spyOn($rootScope, '$emit');
         $translate.refresh();