Added unit test for pkg/cloud/services/secretsmanager

[Madhur97]

What type of PR is this?
/area testing

What this PR does / why we need it:
This PR increases the unit tests coverage for pkg/cloud/services/secretmanager package.

Which issue(s) this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close the issue(s) when PR gets merged):
Part of #2910

Special notes for your reviewer:

Checklist:

• squashed commits
• includes documentation
• adds unit tests
• adds or updates e2e tests

Release note:

Add unit tests for `pkg/cloud/services/secretmanager` package

[k8s-ci-robot]

@Madhur97: This issue is currently awaiting triage.

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[shivi28]

/ok-to-test

[shivi28]

/lgtm

[sedefsavas]

Regarding the duplication comments: we can do a deduplication PR after all tests are merged.

[sedefsavas]

/lgtm
/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: sedefsavas

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