[10.6.X] Update MXNet to 1.5.0

[cmsbuild]

backport of #5592

please test
redo of #5535

[cmsbuild]

A new Pull Request was created by @cmsbuild for branch IB/CMSSW_10_6_X/gcc700.

@cmsbuild, @smuzaffar, @mrodozov, @tulamor can you please review it and eventually sign? Thanks.
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• Backported from [10.6.X] Update MXNet to 1.5.0 #5592

[smuzaffar]

please test
this has already been integrated in CMSSW and cmsdist gcc820 branch. Just testing here to make sure there is nothing wrong with the external build

[cmsbuild]

The tests are being triggered in jenkins.
https://cmssdt.cern.ch/jenkins/job/ib-run-pr-tests/5533/console Started: 2020/04/04 19:12

[cmsbuild]

+1
Tested at: 7f22bc6
https://cmssdt.cern.ch/SDT/jenkins-artifacts/pull-request-integration/PR-a613ee/5533/summary.html
CMSSW: CMSSW_10_6_X_2020-04-04-1100
SCRAM_ARCH: slc7_amd64_gcc700

[cmsbuild]

Comparison job queued.

[cmsbuild]

Comparison is ready
https://cmssdt.cern.ch/SDT/jenkins-artifacts/pull-request-integration/PR-a613ee/5533/summary.html

Comparison Summary:

• No significant changes to the logs found
• Reco comparison results: 0 differences found in the comparisons
• DQMHistoTests: Total files compared: 33
• DQMHistoTests: Total histograms compared: 3212324
• DQMHistoTests: Total failures: 19
• DQMHistoTests: Total nulls: 0
• DQMHistoTests: Total successes: 3211971
• DQMHistoTests: Total skipped: 334
• DQMHistoTests: Total Missing objects: 0
• DQMHistoSizes: Histogram memory added: 0.0 KiB( 32 files compared)
• Checked 137 log files, 14 edm output root files, 33 DQM output files