test: use T.Setenv to set env vars in tests

[Juneezee]

Changes

A testing cleanup.

This PR replaces os.Setenv with t.Setenv. Starting from Go 1.17, we can use t.Setenv to set environment variable in test. The environment variable is automatically restored to its original value when the test and all its subtests complete. This ensures that each test does not start with leftover environment variables from previous completed tests.

func TestFoo(t *testing.T) {
	// before
	key := "ENV"
	originalEnv := os.Getenv(key)
	
	if err := os.Setenv(key, "new value"); err != nil {
		t.Fatal(err)
	}
	defer func() {
		if err := os.Setenv(key, originalEnv); err != nil {
			t.Logf("failed to set env %s back to original value: %v", key, err)
		}
	}()
	
	// after
	t.Setenv(key, "new value")
}

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Release Notes

NONE

[tekton-robot]

Hi @Juneezee. Thanks for your PR.

I'm waiting for a tektoncd 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.

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[dibyom]

/ok-to-test

[dibyom]

Thanks @Juneezee - appreciate the detailed description!
/approve

[tekton-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: dibyom

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[dibyom]

/kind cleanup

[tekton-robot]

The following is the coverage report on the affected files.
Say /test pull-tekton-triggers-go-coverage to re-run this coverage report

File	Old Coverage	New Coverage	Delta
pkg/interceptors/server/server.go	79.3%	81.8%	2.6

[dibyom]

/lgtm