request-cert fails to request signing if already requested and approved

This is my scenario:

1. Create namespace TEST
3. Bring up a new cockroach cluster under TEST
4. Approve the signing requests with `kubectl certificates approve ...`.
4. Delete the namespace TEST
5. Repeat 1-4

The second time around however, the cluster wide approvals still exist but the secrets that stored the certificates in the namespace TEST are gone. So request-cert attempts new requests. This however causes the request-cert to fail "already exists" error. I think I've [found the culprit](https://github.com/cockroachdb/k8s/commit/039524b7d5746c54191e014fa3bc6885a05e5b70#diff-d68d060788a13fec7e4a1ef4c9a3c1efR153) and I'm wondering why the initial request isn't allowed to use previous requests.