Video thumbnails are shown in Media Gallery if they were generated previously, despite being disabled.
Steps to Reproduce:
1. Install and enable FFMpeg
2. Set the following properties in portal-ext.properties
3. Start Liferay.
4. Got to Product Menu > Content & Data > Documents and Media
5. Create a Basic Document from a video
6. Add a Media Gallery widget to a page
7. Assert that you can see the thumbnail
8. Stop the server
9. Set the following properties in portal-ext.properties
10. Start the server again.
11. Check the Media Gallery widget
Video thumbnail is not shown.
Video thumbnail is shown.