fix bug in CURAND.jl's set_stream function.

[norci]

root cause: the parameter stream is not a callable.

[norci]

@maleadt ,
I tried the code in #662 , and got a small error.
I'm not sure if you have fixed it or not.

[codecov]

Codecov Report

Merging #698 (b9c7f91) into master (4eb99b9) will decrease coverage by 0.06%.
The diff coverage is 0.00%.

@@            Coverage Diff             @@
##           master     #698      +/-   ##
==========================================
- Coverage   79.69%   79.62%   -0.07%     
==========================================
  Files         122      122              
  Lines        7356     7356              
==========================================
- Hits         5862     5857       -5     
- Misses       1494     1499       +5     

Impacted Files	Coverage Δ
lib/curand/CURAND.jl	96.29% <0.00%> (ø)
lib/curand/random.jl	90.00% <0.00%> (-2.86%)	⬇️
src/pool/binned.jl	94.78% <0.00%> (-0.87%)	⬇️
src/pool.jl	71.60% <0.00%> (-0.83%)	⬇️

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[maleadt]

Thanks!