Improve verify_cert code coverage (#4111)
Improve verify_cert code coverage (#4111)

* Improve verify_cert code coverage

* Fix lint

smawson/istio,frankbu/istio,geeknoid/istio,smawson/istio,smawson/istio,istio/istio,frankbu/istio,geeknoid/istio,istio/istio,istio/istio,frankbu/istio,istio/istio,geeknoid/istio,istio/istio,smawson/istio,smawson/istio,frankbu/istio,geeknoid/istio,frankbu/istio,smawson/istio,geeknoid/istio,geeknoid/istio,frankbu/istio