LPS-45585 OutOfMemoryError might appear when background index writer threads cannot process DLFileEntries fast enough

Hi Ray,

It's been a while since we talked about this issue (https://github.com/laszlocsontos/liferay-portal/pull/24). Sorry for not getting back to you earlier, my mistake.

Basically this is that former solution you agreed upon with @RobertoDiaz while you were in Madrid, plus I added a new commit for limiting the capacity of the task queue size of the index writer.

Please let me know if you have any concern.

Thanks for reviewing,
László