fix flaky js video test

EDUCATOR-126

common/lib/xmodule/xmodule/js/spec/video/video_caption_spec.js

@@ -68,22 +68,25 @@
                     expect($('.video')).toContainElement('.closed-captions');
                 });
 
-                // flaky test, see LEARNER-689
-                xit('fetch the transcript in HTML5 mode', function(done) {
+                it('fetch the transcript in HTML5 mode', function(done) {
+                    var transcriptURL = '/transcript/translation/en',
+                        transcriptCall;
                     state = jasmine.initializePlayer();
 
                     jasmine.waitUntil(function() {
                         return state.videoCaption.loaded;
                     }).then(function() {
                         expect($.ajaxWithPrefix).toHaveBeenCalledWith({
-                            url: '/transcript/translation/en',
+                            url: transcriptURL,
                             notifyOnError: false,
                             data: void(0),
                             success: jasmine.any(Function),
                             error: jasmine.any(Function)
                         });
-                        expect($.ajaxWithPrefix.calls.mostRecent().args[0].data)
-                            .toBeUndefined();
+                        transcriptCall = $.ajaxWithPrefix.calls.all().find(function(call) {
+                            return call.args[0].url === transcriptURL;
+                        });
+                        expect(transcriptCall.args[0].data).toBeUndefined();
                     }).always(done);
                 });