add missing stream to scalar.is_valid() wherever stream is available

[karthikeyann]

Minor cleanup to utilize stream in scalar.is_valid()

Running scalar.is_valid() on default stream will be blocking all streams until that cudaMemcpy is complete. So, in future when multiple stream are used, this will cause unnecessary global stream sync.

[codecov]

Codecov Report

Merging #9436 (99f7ada) into branch-21.12 (ab4bfaa) will increase coverage by 0.01%.
The diff coverage is 0.00%.

❗ Current head 99f7ada differs from pull request most recent head 1762f27. Consider uploading reports for the commit 1762f27 to get more accurate results

@@               Coverage Diff                @@
##           branch-21.12    #9436      +/-   ##
================================================
+ Coverage         10.79%   10.80%   +0.01%     
================================================
  Files               116      117       +1     
  Lines             18869    19425     +556     
================================================
+ Hits               2036     2098      +62     
- Misses            16833    17327     +494     

Impacted Files	Coverage Δ
python/cudf/cudf/__init__.py	0.00% <0.00%> (ø)
python/cudf/cudf/_lib/__init__.py	0.00% <ø> (ø)
python/dask_cudf/dask_cudf/sorting.py	93.52% <0.00%> (-0.60%)	⬇️
python/cudf/cudf/io/csv.py	0.00% <0.00%> (ø)
python/cudf/cudf/io/hdf.py	0.00% <0.00%> (ø)
python/cudf/cudf/io/orc.py	0.00% <0.00%> (ø)
python/cudf/cudf/_version.py	0.00% <0.00%> (ø)
python/cudf/cudf/core/abc.py	0.00% <0.00%> (ø)
python/cudf/cudf/api/types.py	0.00% <0.00%> (ø)
python/cudf/cudf/io/dlpack.py	0.00% <0.00%> (ø)
... and 61 more

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[karthikeyann]

rerun tests

[karthikeyann]

@gpucibot merge