chronyd从将时间同步到名称已从池中解析的服务器的状态更改为丢失与服务器通信的状态时，如何工作？
CentOS 7
# chronyd -v
chronyd (chrony) version 1.29.1
# grep server /etc/chrony.conf
# Use public servers from the pool.ntp.org project.
server 0.amazon.pool.ntp.org iburst
server 1.amazon.pool.ntp.org iburst
server 2.amazon.pool.ntp.org iburst
server 3.amazon.pool.ntp.org iburst
# Serve time even if not synchronized to any NTP server.
时间未同步
# chronyc sources
210 Number of sources = 4
MS Name/IP address Stratum Poll Reach LastRx Last sample
===============================================================================
^? 45.76.218.213.vultr.com 2 10 0 518d -6679us[-6905us] +/- 40ms
^? v150-95-148-140.a08d.g.ty 2 10 0 745d -105.4s[ +315us] +/- 47ms
^? 45.76.98.188.vultr.com 3 10 0 564d +1031ms[ -242us] +/- 209ms
^? 153-128-30-125.compute.jp 2 10 0 748d -108.1s[-2427us] +/- 37ms