help: Restart Telnet service

run:
      if cli-shell-api existsActive service telnet; then
          port="$(cli-shell-api returnActiveValue service telnet port)"
          listen_address="$(cli-shell-api returnActiveValue service telnet listen-address)"
          echo "Restarting Telnet..."
          /opt/vyatta/sbin/vyatta_update_telnet enable $port $listen_address
          if [[ $? -eq 0 ]]; then
              echo "Success!"
          fi
      else
          echo "Telnet is not configured"
      fi