[GitLab] Fix issue on legacy attributes in certificate when register GitLab Runner

When try to register GitLab runner with command gitlab-runner register : gitlab-runner register : tls: failed to verify certificate: x509: certificate relies on legacy Common Name field, use SANs instead.

It caused by GitLab not support cert verify with legacy certificate attribute. To resolve that problem it need to genearate certificate in server again. And steps will show as below.

1. Generate new certificate and install in GitLab server
   Execute command below in GitLab server:

   export HOSTNAME=home-gitlb-sr01
   export CERT_VALID_DAYS=36500
   export CERT_PATH=/etc/gitlab/ssl
   
   ## Install OpenSSL
   sudo apt install -y openssl
   
   ## Generate RSA key with 2048 length.
   sudo openssl genrsa -out ${HOSTNAME}.key 2048
   
   ## Generate x509 certificate which contain SANs with key generated. 
   sudo openssl req -new -x509 -addext "subjectAltName = DNS:localhost,DNS:${HOSTNAME}" -days ${CERT_VALID_DAYS} -key ${HOSTNAME}.key -out ${HOSTNAME}.crt
   
   ## Backup original certificate and replace with generated one.
   sudo tar -czvf ${CERT_PATH} ${CERT_PATH}.tar.gz
   sudo cp ${HOSTNAME}.crt ${CERT_PATH}/
   
   ## Restart GitLab server to apply new certificate.
   sudo gitlab-ctl reconfigure
   sudo gitlab-ctyl restart

2. Import certificate in Gitlab Runner and apply settings.

   export HOSTNAME=home-gitlb-sr01
   
   ## Get Cert from GitLab server and copy to runner cert directory.
   openssl s_client -showcerts -connect ${HOSTNAME}:443 -servername ${HOSTNAME} < /dev/null 2>/dev/null | openssl x509 -outform PEM > ${HOSTNAME}.crt
   sudo cp ${HOSTNAME}.crt /etc/gitlab-runner/certs/
   
   sudo gitlab-runner register --tls-ca-file=${HOSTNAME}.crt
   sudo gitlab-runner restart
   sudo gitlab-runner run