Fix hang in test_collect_retry
Fix hang in test_collect_retry

jakirkham/dask,mraspaud/dask,mraspaud/dask,wiso/dask,clarkfitzg/dask,dask/dask,pombredanne/dask,jayhetee/dask,simudream/dask,gameduell/dask,jakirkham/dask,blaze/dask,cpcloud/dask,jcrist/dask,pombredanne/dask,ssanderson/dask,ContinuumIO/dask,mrocklin/dask,simudream/dask,jayhetee/dask,jcrist/dask,PhE/dask,cowlicks/dask,dask/dask,clarkfitzg/dask,vikhyat/dask,ContinuumIO/dask,wiso/dask,PhE/dask,mikegraham/dask,mrocklin/dask,vikhyat/dask,chrisbarber/dask,blaze/dask,ssanderson/dask