init: unmount /update after a failed update

packages/sysutils/busybox/scripts/init

@@ -677,6 +677,8 @@ check_out_of_space() {
 do_cleanup() {
   StartProgress spinner "Cleaning up... "
 
+  umount /update 2>/dev/null
+
   if [ -d $UPDATE_ROOT/.tmp/mnt ]; then
     if mountpoint -q $UPDATE_ROOT/.tmp/mnt ; then
       # busybox umount deletes loop device automatically
@@ -938,7 +940,6 @@ check_update() {
   umount /sysroot
   update_file "System" "$UPDATE_SYSTEM" "/flash/$IMAGE_SYSTEM"
   update_bootloader
-  umount /update
   do_cleanup
   do_reboot
 }