[CI] Correct propagation of error codes in GluonNLP-py3-master-gpu-doc

[leezu]

Set -o pipefail for gluon_nlp_job.sh

I'll have to rebuild the docker container after this change.

cc @dmlc/gluon-nlp-team

[codecov]

Codecov Report

Merging #971 into master will increase coverage by 15.86%.
The diff coverage is n/a.

@@             Coverage Diff             @@
##           master     #971       +/-   ##
===========================================
+ Coverage   73.87%   89.74%   +15.86%     
===========================================
  Files          67       67               
  Lines        6423     6423               
===========================================
+ Hits         4745     5764     +1019     
+ Misses       1678      659     -1019

Impacted Files	Coverage Δ
src/gluonnlp/data/batchify/embedding.py	47.69% <0%> (-50.01%)	⬇️
src/gluonnlp/vocab/subwords.py	84.78% <0%> (-2.18%)	⬇️
src/gluonnlp/data/batchify/batchify.py	96.06% <0%> (+0.78%)	⬆️
src/gluonnlp/data/transforms.py	86% <0%> (+1.11%)	⬆️
src/gluonnlp/data/question_answering.py	100% <0%> (+1.66%)	⬆️
src/gluonnlp/model/train/embedding.py	87.17% <0%> (+2.56%)	⬆️
src/gluonnlp/vocab/elmo.py	96.66% <0%> (+3.33%)	⬆️
src/gluonnlp/data/corpora/wikitext.py	100% <0%> (+5.17%)	⬆️
src/gluonnlp/embedding/token_embedding.py	91.96% <0%> (+5.69%)	⬆️
src/gluonnlp/data/stream.py	84.97% <0%> (+7.25%)	⬆️
... and 20 more

[mli]

Job PR-971/1 is complete.
Docs are uploaded to http://gluon-nlp-staging.s3-accelerate.dualstack.amazonaws.com/PR-971/1/index.html

[leezu]

Confirmed based on http://ci.mxnet.io/blue/organizations/jenkins/GluonNLP-py3-master-gpu-doc/detail/PR-967/16/pipeline that the change works correctly