add monitoring to client certs expiration

Client cert /root/cdk/client.crt is not being monitored, when the client cert expires, it'd cause part of the APIs unavailable (for example, metric API)

# find /root/cdk -type f -name "*.crt" -print | egrep -v 'ca.crt$' | xargs -L 1 -t -i bash -c 'openssl x509 -noout -text -in {}|grep After'
bash -c openssl x509 -noout -text -in /root/cdk/client.crt|grep After
            Not After : Feb 19 00:35:10 2023 GMT
bash -c openssl x509 -noout -text -in /root/cdk/server.crt|grep After
            Not After : Aug 23 07:23:53 2023 GMT

$ kubectl logs metrics-server-v0.5.2-7f6f9dd87f-hzz6k -n kube-system -c metrics-server --tail 5
error: You must be logged in to the server (the server has asked for the client to provide credentials ( pods/log metrics-server-v0.5.2-7f6f9dd87f-hzz6k))

$kubectl top nodes
Error from server (ServiceUnavailable): the server is currently unable to handle the request (get nodes.metrics.k8s.io)