MXNet SDK with Status check fix

[johnugeorge]

1. Success/Running status checks are done only for Scheduler replica type. Else, statuses get rewritten for various replicas
2. MXNet SDK is added
3. e2e test test_e2e_mxjob.py is added to CI

[coveralls]

Pull Request Test Coverage Report for Build 2530967617

• 0 of 30 (0.0%) changed or added relevant lines in 1 file are covered.
• 1 unchanged line in 1 file lost coverage.
• Overall coverage decreased (-0.01%) to 39.884%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
pkg/controller.v1/mxnet/mxjob_controller.go	0	30	0.0%

Files with Coverage Reduction	New Missed Lines	%
pkg/controller.v1/mxnet/mxjob_controller.go	1	0%

Totals
Change from base Build 2507080761:	-0.01%
Covered Lines:	2328
Relevant Lines:	5837

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💛 - Coveralls

[terrytangyuan]

Thanks!

/lgtm

[google-oss-prow]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: johnugeorge, terrytangyuan

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