11 minutes mode in RHEL 8 and RHEL 9

Issue

• In RHEL8/9, timedatectl can not be used to check 11 minutes mode is on and working or not.
• Command timedatectl reports "System clock synchronized: yes" even if "rtcsync" is commented in /etc/chrony.conf.

[root@vm80 etc]# grep rtc /etc/chrony.conf
#rtcsync
[root@vm80 etc]# timedatectl
               Local time: Tue 2020-01-21 15:45:55 JST
           Universal time: Tue 2020-01-21 06:45:55 UTC
                 RTC time: Tue 2020-01-21 06:45:54
                Time zone: Asia/Tokyo (JST, +0900)
System clock synchronized: yes       <===
              NTP service: active
          RTC in local TZ: no

• Unreliable RTC synchronization (11-minute mode) in RHEL 8 (prior to kernel-4.18.0-348.el8), it may take a very long time to actually set the RTC. RHEL 9 doesn't have this issue.
• RTC synchronization (11-minute mode) doesn't work on KVM