Fix sporadic failure in test_nrt_refct
Fix sporadic failure in test_nrt_refct

(hopefully)

stonebig/numba,seibert/numba,cpcloud/numba,stonebig/numba,jriehl/numba,stuartarchibald/numba,stuartarchibald/numba,IntelLabs/numba,stonebig/numba,seibert/numba,IntelLabs/numba,stuartarchibald/numba,IntelLabs/numba,sklam/numba,sklam/numba,gmarkall/numba,numba/numba,IntelLabs/numba,sklam/numba,numba/numba,gmarkall/numba,stonebig/numba,jriehl/numba,numba/numba,numba/numba,jriehl/numba,jriehl/numba,seibert/numba,jriehl/numba,gmarkall/numba,gmarkall/numba,stonebig/numba,stuartarchibald/numba,sklam/numba,cpcloud/numba,seibert/numba,seibert/numba,sklam/numba,gmarkall/numba,IntelLabs/numba,cpcloud/numba,cpcloud/numba,numba/numba,stuartarchibald/numba,cpcloud/numba