This will improve our tests and shutdown since we can then shut down the executor and interrupt long running threads.
SyncStrategy should have a close so it can abort earlier on shutdown.
This will depend on SOLR-3870 to close down the executor.
Due to the impact on jenkins tests, I'd actually like to put this straight to 4.0 before the RC. I'd be more comfortable if 4.0 ran smoothly on freebsd jenkins. The changes themselves are fairly simple and easy to review. Patch in a moment.
[branch_4x commit] Mark Robert Miller
SOLR-3871: SyncStrategy should use an executor for the threads it creates to request recoveries.
SOLR-3870: SyncStrategy should have a close so it can abort earlier on shutdown.
Closed after release.