Replace dummy client with fake client

[tenzen-y]

What this PR does / why we need it:
I replaced dummy_client for reconciler with the fake client.
Our dummy_client implements client.Client interface and maintaining dummy_clinety is hard.
For example, controller runtime expands that interface since v0.14. And then, we faced unimplemented errors when we upgraded the controller runtime version.

#1817

 Error: test_job/reconciler.v1/test_job/test_job_reconciler.go:46:46: cannot use dummy_client (variable of type *DummyClient) as type client.Client in argument to common_reconciler.BareJobReconciler:
	*DummyClient does not implement client.Client (missing SubResource method)
Error: test_job/reconciler.v1/test_job/test_job_reconciler.go:49:46: cannot use dummy_client (variable of type *DummyClient) as type client.Client in argument to common_reconciler.BarePodReconciler:
	*DummyClient does not implement client.Client (missing SubResource method)
Error: test_job/reconciler.v1/test_job/test_job_reconciler.go:52:50: cannot use dummy_client (variable of type *DummyClient) as type client.Client in argument to common_reconciler.BareServiceReconciler:
	*DummyClient does not implement client.Client (missing SubResource method)

Which issue(s) this PR fixes (optional, in Fixes #<issue number>, #<issue number>, ... format, will close the issue(s) when PR gets merged):
Part-of #1816

Checklist:

• Docs included if any changes are user facing

[coveralls]

Pull Request Test Coverage Report for Build 5133143951

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 2 unchanged lines in 1 file lost coverage.
• Overall coverage increased (+0.2%) to 33.913%

---

Files with Coverage Reduction	New Missed Lines	%
pkg/controller.v1/mpi/mpijob_controller.go	2	77.5%

Totals
Change from base Build 5132051603:	0.2%
Covered Lines:	3336
Relevant Lines:	9837

---

💛 - Coveralls

[tenzen-y]

/assign @johnugeorge

[tenzen-y]

I found a new flaky test....

#1819

[johnugeorge]

Agree. Thanks @tenzen-y

/lgtm
/approve

[google-oss-prow]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: johnugeorge, tenzen-y

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