[pytorch] Fix PtNDArray interoperability with other engine

[frankfliu]

Change-Id: If0d602c897937b25a9d1b1808568a9bb4fbc582e

Description

Brief description of what this PR is about

• If this change is a backward incompatible change, why must this change be made?
• Interesting edge cases to note here

[codecov-commenter]

Codecov Report

Merging #1270 (3805f87) into master (9aaaa66) will increase coverage by 0.01%.
The diff coverage is 78.94%.

@@             Coverage Diff              @@
##             master    #1270      +/-   ##
============================================
+ Coverage     71.99%   72.01%   +0.01%     
- Complexity     5114     5117       +3     
============================================
  Files           473      473              
  Lines         21913    21945      +32     
  Branches       2345     2347       +2     
============================================
+ Hits          15777    15804      +27     
- Misses         4932     4937       +5     
  Partials       1204     1204              

Impacted Files	Coverage Δ
.../src/main/java/ai/djl/dlr/engine/DlrNDManager.java	78.37% <0.00%> (ø)
.../src/main/java/ai/djl/ml/xgboost/XgbNDManager.java	75.51% <0.00%> (ø)
...src/main/java/ai/djl/mxnet/engine/MxNDManager.java	87.12% <0.00%> (ø)
...n/java/ai/djl/onnxruntime/engine/OrtNDManager.java	72.22% <0.00%> (ø)
...n/java/ai/djl/paddlepaddle/engine/PpNDManager.java	87.50% <0.00%> (ø)
...ain/java/ai/djl/tensorflow/engine/TfNDManager.java	89.31% <0.00%> (ø)
...ain/java/ai/djl/tflite/engine/TfLiteNDManager.java	80.76% <0.00%> (ø)
...c/main/java/ai/djl/pytorch/engine/PtNDArrayEx.java	85.54% <89.79%> (-0.27%)	⬇️
...c/main/java/ai/djl/pytorch/engine/PtNDManager.java	93.18% <100.00%> (ø)

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