Reduce number of pods created for local PV stress test

[msau42]

What this PR does / why we need it:
Local PV stress test is flaking. Failed runs show that test is timing out at 47/50 pods. Reduce the number of pods created by the test so that it's not so close to the max timeout.

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

Special notes for your reviewer:
I'll need to investigate further to see why processing the pods is so slow and ways to speed it up. But for now, try to reduce flaking.

Release note:

NONE

[msau42]

/assign @verult

[verult]

/lgtm

[msau42]

/test pull-kubernetes-verify

[fejta-bot]

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[jeffvance]

/lgtm

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: jeffvance, msau42, verult

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[msau42]

/retest

[k8s-github-robot]

Automatic merge from submit-queue (batch tested with PRs 59310, 60424, 60308, 60436, 60020). If you want to cherry-pick this change to another branch, please follow the instructions here.