Update the name of PVC in train API

[helenxie-bit]

What this PR does / why we need it:
According to the discussion, this PR updates the name of PVC in train API to have pvc_name == job_name. In this case, each job will have a separate PVC.

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:

[coveralls]

Pull Request Test Coverage Report for Build 10158325600

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.1%) to 34.944%

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Totals
Change from base Build 10131041132:	0.1%
Covered Lines:	3949
Relevant Lines:	11301

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💛 - Coveralls

[helenxie-bit]

/area gsoc

[andreyvelich]

Thank you for updating this @helenxie-bit!
/lgtm
/approve

[google-oss-prow]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: andreyvelich

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