The whiteboard portlet loose synchronization after some minutes of inactivity.

When the users stop using the portlet for some minutes and later continue using it, the portlet has already loose the synchronization between users and also loose all the objects of that was in the whiteboard.

Preconditions
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2 Users should be previously created.
User1 Administrator
User2 Administrator

REPRODUCIBILITY LEVEL:
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Always

STEPS:
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Steps
1.Open the Liferay APP with the Collaboration portlet with user 1.
2. Open the Liferay APP with the Collaboration portlet with user 2.(keep checking the window)
3. Using the window logged with user 1, Click on the “Add a Rectangle” icon.
4. Click on the Fill button and select a color.
5. Click on the “Add a Text” icon.
6. Type “Test” and click on the “Save” Button.
7. Add 3 more objects.
8. Wait for approximately 10 minutes without moving or adding objects
9. Move and add some new objects.
* note: that whiteboard is not longer synchronized with other users
10. Reload the page.
         *Note: that all, except the last added objects are deleted.

CURRENT RESULT:
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The portlet loose synchronization after some minutes of inactivity, also the whiteboard portlet deleted all the created objects after reload the page.
https://www.screencast.com/t/nFMnDKQuI

EXPECTED RESULT:
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The portlet should not lose synchronization after some minutes of inactivity, also the whiteboard portlet should not delete all the created objects after reload the page. The portlet should only lose synchronization is the session expires.