cert-checker: Exit non-zero on check failure

[beautifulentropy]

Fixes #8748

[github-actions]

@beautifulentropy, this PR appears to contain configuration and/or SQL schema changes. Please ensure that a corresponding deployment ticket has been filed with the new values.

[github-actions]

@beautifulentropy, this PR appears to contain configuration and/or SQL schema changes. Please ensure that a corresponding deployment ticket has been filed with the new values.

[jsha]

Note: The PR description says "Fixes #8748", but that issue also says:

> Ensure each of our test profiles is exercised by integration tests (otherwise, why have that profile in CI?).

We should either change the PR description to "Part of #8748", or file a separate issue to exercise the modern profile in CI.

[jsha]

Oop, nevermind - I see we do issue under the modern profile:

boulder/test/integration/issuance_test.go

Lines 158 to 161 in 7c321ac

	res, err = authAndIssue(client, key, idents, true, "modern")
	test.AssertNotError(t, err, "failed to issue under modern profile")
	test.AssertEquals(t, res.Order.Profile, "modern")
	modern := res.certs[0]