Incorrect calculation of block count

Block count were returned based of KB, but blocks of 1MB were written !

Signed-off-by: Damien Gustave <delovan@gmail.com>

packer_templates/_common/minimize.sh

@@ -5,14 +5,12 @@ case "$PACKER_BUILDER_TYPE" in
 esac
 
 # Whiteout root
-count=$(df --sync -kP / | tail -n1  | awk -F ' ' '{print $4}')
-count=$(($count-1))
+count=$(df --sync -kP / | tail -n1  | awk -F ' ' '{printf("%d",($4-1)/1024-1)}')
 dd if=/dev/zero of=/tmp/whitespace bs=1M count=$count || echo "dd exit code $? is suppressed";
 rm /tmp/whitespace
 
 # Whiteout /boot
-count=$(df --sync -kP /boot | tail -n1 | awk -F ' ' '{print $4}')
-count=$(($count-1))
+  count=$(df --sync -kP /boot | tail -n1  | awk -F ' ' '{printf("%d",($4-1)/1024-1)}')
 dd if=/dev/zero of=/boot/whitespace bs=1M count=$count || echo "dd exit code $? is suppressed";
 rm /boot/whitespace