Handle Horovod Import Error Bug

[NihalHarish]

Description of changes:

• import horovod.torch as hvd does not raise an ImportError if it is not present.
• We need to redundantly import torch to see if we're running in a env with pytorch present

Style and formatting:

I have run pre-commit install && pre-commit run --all-files to ensure that auto-formatting happens with every commit.

Issue number, if available

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[codecov-commenter]

Codecov Report

Merging #518 (63f7309) into master (d701086) will decrease coverage by 1.26%. The diff coverage is 0.00%.

@@            Coverage Diff             @@
##           master     #518      +/-   ##
==========================================
- Coverage   76.39%   75.13%   -1.27%     
==========================================
  Files         127      117      -10     
  Lines       11110    10585     -525     
==========================================
- Hits         8488     7953     -535     
- Misses       2622     2632      +10     

Impacted Files	Coverage Δ
smdebug/core/utils.py	79.94% <0.00%> (-0.82%)	:arrow_down:
smdebug/pytorch/utils.py	45.23% <0.00%> (-35.72%)	:arrow_down:
smdebug/tensorflow/version_check.py	75.00% <0.00%> (-25.00%)	:arrow_down:
smdebug/analysis/utils.py	64.70% <0.00%> (-15.69%)	:arrow_down:
smdebug/exceptions.py	69.04% <0.00%> (-11.91%)	:arrow_down:
smdebug/core/reduction_config.py	88.31% <0.00%> (-7.80%)	:arrow_down:
smdebug/core/singleton_utils.py	79.41% <0.00%> (-5.89%)	:arrow_down:
smdebug/core/locations.py	86.11% <0.00%> (-5.56%)	:arrow_down:
smdebug/core/tfrecord/record_writer.py	95.00% <0.00%> (-5.00%)	:arrow_down:
smdebug/core/tensor.py	79.03% <0.00%> (-4.84%)	:arrow_down:
... and 22 more

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