lib: Fix U-Boot check_bootcounter

Since addition of EFI support, the bootcounter variables are shared between
the different bootloader check parts.
Variables set using read function in pipe subshell are not available
outside of this subshell, and so unset for the rest of the function.

Signed-off-by: Frédéric Danis <frederic.danis@collabora.com>

update-manager-common.sh

@@ -326,20 +326,22 @@ EFIBOOTDIR="/boot/efi/loader/entries"
 check_bootcounter()
 {
 	if [ -f /boot/uboot.cnt ]; then
-		od -t x1 -An /boot/uboot.cnt | (
-			read -r m ver cnt uflag
-
-			# Special case for old format
-			if [ "$m" = "bc" ]; then
-				cnt="$ver"
-				ver="00"
-				# NB: due the bug in legacy U-Boot -- it always create the uboot.cnt and
-				# increase the counter, so it is not possible to detect the upgrade
-				# state properly. Hence set the upgrade state for the legacy into
-				# requested value to avoid failures.
-				uflag="${4:-1}"
-			fi
-		)
+		uboot_counter=$(od -t x1 -An /boot/uboot.cnt)
+		m=$(echo $uboot_counter | cut -d ' ' -f 1)
+		# Special case for old format
+		if [ "$m" = "bc" ]; then
+			cnt=$(echo $uboot_counter | cut -d ' ' -f 2)
+			ver="00"
+			# NB: due the bug in legacy U-Boot -- it always create the uboot.cnt and
+			# increase the counter, so it is not possible to detect the upgrade
+			# state properly. Hence set the upgrade state for the legacy into
+			# requested value to avoid failures.
+			uflag="${4:-1}"
+		else
+			ver=$(echo $uboot_counter | cut -d ' ' -f 2)
+			cnt=$(echo $uboot_counter | cut -d ' ' -f 3)
+			uflag=$(echo $uboot_counter | cut -d ' ' -f 4)
+		fi
 	elif [ -f ${EFIBOOTDIR}/ostree-0-2*.conf ]; then
 		m="$1"
 		ver="${2:-00}"