Remove cow file early for non-persistent systems

The kernel has an open file handle after setting up the mapping. We can
remove it early to make sure it is gone on shutdown.

This helps to keep the cow_device clean for non-persistent systems where
cow_directory contains a version specific string.

Signed-off-by: Christian Hesse <mail@eworm.de>

archiso/initcpio/hooks/archiso

@@ -33,6 +33,10 @@ _mnt_dmsnapshot() {
 
     dmsetup create ${dm_snap_name} --table "0 ${ro_dev_size} snapshot ${ro_dev} ${rw_dev} ${cow_persistent} ${cow_chunksize}"
 
+    if [[ "${cow_persistent}" != "P" ]]; then
+        rm -f "/run/archiso/cowspace/${cow_directory}/${img_name}.cow"
+    fi
+
     _mnt_dev "/dev/mapper/${dm_snap_name}" "${newroot}${mnt}" "-w" "defaults"
     echo $(readlink -f /dev/mapper/${dm_snap_name}) >> /run/archiso/used_block_devices
 }