target/realtek: fix upgrade hang

(cherry picked from commit fc2db101bcf238dc2faad6ed5a24ffbbeb5921fc)

package/base-files/files/lib/upgrade/stage2

@@ -115,8 +115,8 @@ killall -9 ash
 kill_remaining TERM
 sleep 3
 sync
-/usr/bin/umount -R -d /mnt
-/usr/bin/umount -R -d /overlay
+/usr/bin/umount -R -d /mnt &
+sleep 5
 kill_remaining KILL 1
 
 sleep 1
@@ -135,7 +135,7 @@ fi
 
 grep /overlay /proc/mounts > /dev/null && {
 	/bin/mount -o noatime,remount,ro /overlay
-	/bin/umount -l /overlay
+	/usr/bin/umount -R -d -l /overlay || /bin/umount -l /overlay
 }
 
 # Exec new shell from ramfs

target/linux/realtek/base-files/etc/init.d/rtk_upgrade

@@ -5,21 +5,27 @@ START=14
 
 split_opkg_status() {
 	local line
-	local of=/dev/null
+	local gap=1
+	exec 3>/dev/null
 	rm -rf $2
 	mkdir -p $2
 	cat $1 | while read; do
 		line="$REPLY"
 		if [ -z "$line" ]; then
-			echo >>$of
-			of=/dev/null
+			echo >&3
+			exec 3>&-
+			exec 3>/dev/null
+			gap=1
 		else
-			if [ "x/dev/null" = "x$of" ] && echo "$line" | grep -q "^Package: "; then
-				of=$2/`echo "$line"|cut -d' ' -f2`
+			if [ "x1" = "x$gap" ] && echo "$line" | grep -q "^Package: "; then
+				exec 3>&-
+				exec 3>$2/`echo "$line"|cut -d' ' -f2`
+				gap=0
 			fi
-			echo "$line" >>$of
+			echo "$line" >&3
 		fi
 	done
+	exec 3>&-
 }
 
 split_both_status() {

target/linux/realtek/base-files/lib/upgrade/platform.sh

@@ -1,7 +1,7 @@
 
 # bins for install_a
 RAMFS_COPY_BIN="/usr/bin/cat /usr/bin/chmod /usr/bin/cp /usr/bin/dd \
-/usr/bin/echo /usr/bin/mkdir /usr/bin/rm"
+/usr/bin/echo /usr/bin/mkdir /usr/bin/rm /usr/bin/umount"
 
 platform_check_image() {
 	echo "platform_check_image"