Race in mdadm udev timer rules

Issue

• Issues with mdadm activation at boot. Below errors seen:

  Sep 13 15:14:01 host systemd: Timed out stoppping /dev/md124.
  Sep 13 15:14:01 host systemd: Timed out stoppping /sys/devices/virtual/block/md124.
  Sep 13 15:14:01 host systemd: Timed out stoppping /dev/md/var.
  [...]
  Sep 13 15:12:31 host systemd: Starting system-mdadm\x2dlast\x2dresort.slice.
  Sep 13 15:12:31 host systemd: Starting Activate md array even though degraded...
  [...]
  Sep 28 03:29:26 host systemd[1]: Unmounting /var...
  Sep 28 03:29:26 host umount[2716]: umount: /var: target is busy.
  Sep 28 03:29:26 host umount[2716]: (In some cases useful info about processes that use
  Sep 28 03:29:26 host umount[2716]: the device is found by lsof(8) or fuser(1))
  Sep 28 03:29:26 host systemd[1]: var.mount mount process exited, code=exited status=32
  

• Software RAID system doesn't boot after first drive fails due to hardware error.