Fix image name for example webhook, and other nitpicks

Also bump example container versions to v3.0.0, and use
k8s.gcr.io/sig-storage instead of quay.io/k8scsi.

deploy/kubernetes/webhook-example/create-cert.sh

@@ -122,5 +122,5 @@ echo ${serverCert} | openssl base64 -d -A -out ${tmpdir}/server-cert.pem
 kubectl create secret generic ${secret} \
         --from-file=key.pem=${tmpdir}/server-key.pem \
         --from-file=cert.pem=${tmpdir}/server-cert.pem \
-        --dry-run -o yaml |
+        --dry-run=client -o yaml |
     kubectl -n ${namespace} apply -f -