block_retrieval_worker_test: Added correct check at the end of Shutdown test.
block_retrieval_worker_test: Added correct check at the end of Shutdown test.

keybase/client,keybase/client,keybase/kbfs,keybase/client,keybase/kbfs,keybase/client,keybase/kbfs,keybase/client,keybase/client,keybase/client,keybase/client,keybase/client,keybase/kbfs,keybase/client,keybase/client,keybase/client