SMDDP should use size() and rank() for TF jobs

[ndodda-amazon]

Description of changes:

Fixing a bug introduced by #425 where get_size() and get_rank() were used for all jobs, when the correct API for TF jobs is actually is actually size() and rank().

This bug was missed before because we do not have any tests that run TF SMDDP jobs.

Style and formatting:

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

Issue number, if available

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[codecov-io]

Codecov Report

Merging #451 (d9598e1) into master (0131559) will decrease coverage by 0.57%. The diff coverage is 25.00%.

@@            Coverage Diff             @@
##           master     #451      +/-   ##
==========================================
- Coverage   65.86%   65.28%   -0.58%     
==========================================
  Files         161      162       +1     
  Lines       12747    12889     +142     
==========================================
+ Hits         8396     8415      +19     
- Misses       4351     4474     +123     

Impacted Files	Coverage Δ
smdebug/core/utils.py	78.49% <25.00%> (ø)
smdebug_rules/generic/create_xgboost_report.py	17.70% <0.00%> (-8.39%)	:arrow_down:
smdebug/pytorch/hook.py	76.03% <0.00%> (-0.64%)	:arrow_down:
smdebug/core/writer.py	90.09% <0.00%> (ø)
smdebug_rules/generic/__init__.py	100.00% <0.00%> (ø)
smdebug_rules/generic/constants.py	100.00% <0.00%> (ø)

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[ChoiByungWook]

User is reporting a similar issue: https://github.com/aws/sagemaker-python-sdk/issues/2170