cmd/mcp_test: use t.Setenv to prevent env var leak across tests

[Elvand-Lie]

TestMCP_StartWriteable sets FUNC_ENABLE_MCP_WRITE via os.Setenv but never cleans it up. Since Go runs all tests in a package within the same process, this leaked env var persists for subsequent tests.

Replace os.Setenv with t.Setenv, which automatically restores the original value when the test finishes. Remove the now-unused os import.

Changes

• Replace os.Setenv with t.Setenv in TestMCP_StartWriteable to auto-restore the env var after the test
• Remove unused "os" import from cmd/mcp_test.go

Fixes #3686

Release Note

NONE

[knative-prow]

@Elvand-Lie: The label(s) kind/<kind> cannot be applied, because the repository doesn't have them.

Details

In response to this:

TestMCP_StartWriteable sets FUNC_ENABLE_MCP_WRITE via os.Setenv but never cleans it up. Since Go runs all tests in a package within the same process, this leaked env var persists for subsequent tests.

Replace os.Setenv with t.Setenv, which automatically restores the original value when the test finishes. Remove the now-unused os import.

Fixes #3686

Changes

/kind

Fixes #

Release Note

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[knative-prow]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: Elvand-Lie
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[linux-foundation-easycla]

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[knative-prow]

Welcome @Elvand-Lie! It looks like this is your first PR to knative/func 🎉

[knative-prow]

Hi @Elvand-Lie. Thanks for your PR.

I'm waiting for a knative member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work.

Regular contributors should join the org to skip this step.

Once the patch is verified, the new status will be reflected by the ok-to-test label.

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[Elvand-Lie]

/kind bug

[knative-prow]

@Elvand-Lie: Cannot trigger testing until a trusted user reviews the PR and leaves an /ok-to-test message.

Details

In response to this:

/ok-to-test

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