fix(operator): Use Patch to update TrainJob status

[astefanutti]

What this PR does / why we need it:

It happens some status update are missed for a TrainJob when the owned JobSet rapidly updates because of conflicts.

This PR changes to patch TrainJob status instead of update to avoid those conflicts.

Checklist:

• Docs included if any changes are user facing

[coveralls]

Pull Request Test Coverage Report for Build 19738925925

Details

• 0 of 5 (0.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-0.04%) to 51.435%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
pkg/controller/trainjob_controller.go	0	5	0.0%

Totals
Change from base Build 19735962968:	-0.04%
Covered Lines:	1237
Relevant Lines:	2405

---

💛 - Coveralls

[tenzen-y]

AFAIK, the SSA sub resource support has already been done: kubernetes-sigs/controller-runtime#3321

Is this comment right?

[tenzen-y]

Oh, this has not been released, yet.

[tenzen-y]

Thank you!

/lgtm
/approve

[google-oss-prow]

[APPROVALNOTIFIER] This PR is APPROVED

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

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[tenzen-y]

/cherry-pick release-2.1

[google-oss-robot]

@tenzen-y: new pull request created: #3012

Details

In response to this:

/cherry-pick release-2.1

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