check PEERNTP variable before loading existing dhclient files
    
    The /etc/dhcp/dhclient.d/chrony.sh script creates files with NTP servers
    from DHCP only if the PEERNTP variable is not set to "no" (e.g. in
    /etc/sysconfig/network). If the variable was set after the files were
    already created, the chronyd service would still use the NTP servers
    until the files were removed (e.g. after network restart).
    
    Modify the chrony-helper script to check the variable before loading
    any servers from dhclient files. Setting the variable and restarting
    the chronyd service should now have an immediate effect.