Emit play_video event after seek_video event

(cherry picked from commit 46797666)

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

@@ -78,6 +78,13 @@
                 new_time: 1,
                 type: 'any'
             });
+            expect(state.videoEventsPlugin.emitPlayVideoEvent).toBeTruthy();
+        });
+
+        it('can emit "play_video" event after "seek_video" event ', function() {
+            state.videoEventsPlugin.emitPlayVideoEvent = false;
+            state.el.trigger('seek', [1, 0, 'any']);
+            expect(state.videoEventsPlugin.emitPlayVideoEvent).toBeTruthy();
         });
 
         it('can emit "stop_video" event', function() {

common/lib/xmodule/xmodule/js/src/video/09_events_plugin.js

@@ -94,6 +94,7 @@
                     new_time: time,
                     type: type
                 });
+                this.emitPlayVideoEvent = true;
             },
 
             onSpeedChange: function(event, newSpeed, oldSpeed) {