v1.3.x- backport of v1.4.x Travis CI configuration

[perdasilva]

Description

Currently the Travis CI configuration for branch v1.3.x times out.
This PR brings the simplified configuration found in branch v1.4.x to unblock the the Travis CI PR check.

Checklist

Essentials

Please feel free to remove inapplicable items for your PR.

• The PR title starts with [MXNET-$JIRA_ID], where $JIRA_ID refers to the relevant JIRA issue created (except PRs with tiny changes)
• Changes are complete (i.e. I finished coding on this PR)
• All changes have test coverage:
• Unit tests are added for small changes to verify correctness (e.g. adding a new operator)
• Nightly tests are added for complicated/long-running ones (e.g. changing distributed kvstore)
• Build tests will be added for build configuration changes (e.g. adding a new build option with NCCL)
• Code is well-documented:
• For user-facing API changes, API doc string has been updated.
• For new C++ functions in header files, their functionalities and arguments are documented.
• For new examples, README.md is added to explain the what the example does, the source of the dataset, expected performance on test set and reference to the original paper if applicable
• Check the API doc at http://mxnet-ci-doc.s3-accelerate.dualstack.amazonaws.com/PR-$PR_ID/$BUILD_ID/index.html
• To the my best knowledge, examples are either not affected by this change, or have been fixed to be compatible with this change

Changes

Comments

The CI/Jenkins check will fail. The PR fixing this issue is #13562. We should merge this PR first, then re-trigger the other.

[perdasilva]

@mxnet-label-bot add [pr-awaiting-review, ci]

[lebeg]

awesome

[marcoabreu]

Jenkins is broken and disregarded for this PR since the scope is fixing Travis. Travis is properly working, thus merging.