JCR-2225: The total amount of indexing threads should remain consistent

Problem analysis
	- To be backward compatible with the previous mode which was mono threaded, we had to stop all the indexing threads when one thread gets an exception, the problem here was the fact that we had still one thread keeping indexing even if an exception has already occurred.

Fix description
	- If an exception occurs we interrupt explicitly all the indexing thread such that they all will stop indexing the content, we then get back the expected behavior and we have a consistent amount of indexing threads