Handle source/sink/deco cancellation cleanly.

Currently, sources and sinks only throw IOExceptions. When reconfiguring nodes, we may want to cancel sources/sinks that are in constant failure mode by allowing them to be interrupted. The currenty fixes related to FLUME-37 avoid but do not completely solve all the potential hangs.

The proper way to handle this is to throws InterruptedException to all sources/sinks/decos API calls. This will allow cancelations to happen and propagate up sink chains. This will also hopefully allow us to have a cleaner locking discipline which will hopefully eliminate certain races.