We had a "mount -o remount,rw none /" that was setting back 'relatime',
although we had set 'noatime' at initrd mount. Removing the word 'none' fixed
it.
Specifying a device (in this case 'none'), makes mount to forget previous
device options. According to manpage, it says not to read fstab or mtab. But the
effect is that of setting 'relatime', if it was mounted 'noatime.