Changed code to disable k_truss on CUDA 11.4 differently

[rlratzel]

Changed code to disable k_truss on CUDA 11.4 to not use numba.cuda.runtime.get_version() at import time since this creates a CUDA context which breaks dask LocalCUDACluster init (causes a nccl init invaid usage exception).

This code change results in almost the same UX as before, except explicit imports of the k_truss module no longer raise the exception immediately, and instead raise only when a k_truss algo is called.

Tested by ensuring unit tests for the conditional enabling of k_truss still work and also checked that a LocalCUDACluster could properly be created.

Also changed dask_client fixture to module since session was not compatible with tests that tried to create a LocalCUDACluster independently within the same session (rmat tests).

cc @cjnolet @pentschev

[codecov-commenter]

Codecov Report

Merging #1811 (e1222e4) into branch-21.10 (bf64c2c) will increase coverage by 9.85%.
The diff coverage is n/a.

@@               Coverage Diff                @@
##           branch-21.10    #1811      +/-   ##
================================================
+ Coverage         59.85%   69.70%   +9.85%     
================================================
  Files                77      139      +62     
  Lines              3547     8599    +5052     
================================================
+ Hits               2123     5994    +3871     
- Misses             1424     2605    +1181     

Impacted Files	Coverage Δ
python/cugraph/cugraph/__init__.py	100.00% <ø> (ø)
python/cugraph/cugraph/_version.py	44.80% <ø> (ø)
python/cugraph/cugraph/centrality/__init__.py	100.00% <ø> (ø)
...graph/cugraph/centrality/betweenness_centrality.py	90.00% <ø> (ø)
python/cugraph/structure/hypergraph.py
python/cugraph/link_prediction/wjaccard.py
python/cugraph/proto/__init__.py
python/cugraph/community/spectral_clustering.py
...raph/structure/graph_implementation/simpleGraph.py
python/cugraph/layout/__init__.py
... and 202 more

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[BradReesWork]

@gpucibot merge