support make test on darwin

[lowang-bh]

What this PR does / why we need it:

run make test on darwin os

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

Checklist:

• Docs included if any changes are user facing

[tenzen-y]

Thank you for creating this PR!

[tenzen-y]

Thanks!
/lgtm
/assign @terrytangyuan @johnugeorge @gaocegege

[coveralls]

Pull Request Test Coverage Report for Build 5230475108

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 11 unchanged lines in 2 files lost coverage.
• Overall coverage decreased (-0.07%) to 33.791%

---

Files with Coverage Reduction	New Missed Lines	%
pkg/controller.v1/mpi/mpijob_controller.go	2	77.22%
pkg/controller.v1/pytorch/pytorchjob_controller.go	9	58.19%

Totals
Change from base Build 5222257528:	-0.07%
Covered Lines:	3324
Relevant Lines:	9837

---

💛 - Coveralls

[johnugeorge]

/approve

[google-oss-prow]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: johnugeorge, lowang-bh

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