WIP: add unit test for mxjob controller

[zw0610]

What this PR does / why we need it:

To improve the overall test coverage by adding unit tests for mxjob controller

Which issue(s) this PR fixes (optional, in Fixes #<issue number>, #<issue number>, ... format, will close the issue(s) when PR gets merged):
Fixes #1497

Checklist:

• Adding job test form v1beta1

[aws-kf-ci-bot]

Skipping CI for Draft Pull Request.
If you want CI signal for your change, please convert it to an actual PR.
You can still manually trigger a test run with /test all

[google-oss-prow]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: zw0610

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• OWNERS [zw0610]

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[coveralls]

Pull Request Test Coverage Report for Build 1661935931

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 2 unchanged lines in 1 file lost coverage.
• Overall coverage increased (+1.5%) to 38.26%

---

Files with Coverage Reduction	New Missed Lines	%
pkg/controller.v1/mpi/mpijob_controller.go	2	75.16%

Totals
Change from base Build 1660952137:	1.5%
Covered Lines:	2348
Relevant Lines:	6137

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💛 - Coveralls

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.