Code review comment for lp:~raharper/curtin/trunk.fix-lvm-over-raid

The log messages of sysfs write failures look like this:

[ 64.954808] cloud-init[1435]: mdadm: (non-fatal) write to /sys/class/block/md2/md/sync_max failed [Errno 16] Device or resource busy
[ 65.302878] cloud-init[1435]: mdadm: (non-fatal) write to /sys/class/block/md3/md/sync_action failed [Errno 13] Permission denied: '/sys/class/block/md3/md/sync_action'
[ 65.305867] cloud-init[1435]: mdadm: (non-fatal) write to /sys/class/block/md3/md/sync_max failed [Errno 13] Permission denied: '/sys/class/block/md3/md/sync_max'