[CX] CouchbaseConnector.close() doesn't exit normally, leaving CleanupThread running

Running feeds: lifecycle-MB-20315 locally, CouchbaseConnector.close() does not exit normally, which leaves the cleanup thread running (before http://review.couchbase.org/#/c/66930 it locks up a CPU in a spin).

The exception observed is as follows:

2016-08-22 04:06:57,745 ERROR [pool-6-thread-1] runtime.AdapterExecutor (AdapterExecutor.java:run(60)) - Exception during feed ingestion
org.apache.hyracks.api.exceptions.HyracksDataException: Interrupted while waiting for subscription to complete.
at org.apache.asterix.external.util.ExternalDataExceptionUtils.suppressIntoHyracksDataException(ExternalDataExceptionUtils.java:48)
at org.apache.asterix.external.dataflow.FeedRecordDataFlowController.start(FeedRecordDataFlowController.java:117)
at org.apache.asterix.external.dataset.adapter.FeedAdapter.start(FeedAdapter.java:36)
at org.apache.asterix.external.feed.runtime.AdapterExecutor.run(AdapterExecutor.java:56)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at java.lang.Thread.run(Thread.java:745)
Caused by: java.lang.RuntimeException: Interrupted while waiting for subscription to complete.
at rx.observables.BlockingObservable.awaitForComplete(BlockingObservable.java:477)
at rx.observables.BlockingObservable.blockForSingle(BlockingObservable.java:449)
at rx.observables.BlockingObservable.single(BlockingObservable.java:331)
at com.couchbase.analytics.CouchbaseConnector.stop(CouchbaseConnector.java:156)
at com.couchbase.analytics.CouchbaseConnector.close(CouchbaseConnector.java:73)
at org.apache.asterix.external.dataflow.FeedRecordDataFlowController.start(FeedRecordDataFlowController.java:114)
... 5 more
Caused by: java.lang.InterruptedException
at java.util.concurrent.locks.AbstractQueuedSynchronizer.acquireSharedInterruptibly(AbstractQueuedSynchronizer.java:1302)
at java.util.concurrent.CountDownLatch.await(CountDownLatch.java:231)
at rx.observables.BlockingObservable.awaitForComplete(BlockingObservable.java:470)
... 10 more