backuptool: we are now on 6.0

Change-Id: I2ea25063c467c608ca94e9090203d21f4c4b7177
diff --git a/prebuilt/bin/backuptool.sh b/prebuilt/bin/backuptool.sh
index e72e462..ad957e7 100755
--- a/prebuilt/bin/backuptool.sh
+++ b/prebuilt/bin/backuptool.sh
@@ -5,7 +5,7 @@
 
 export C=/tmp/backupdir
 export S=/system
-export V=5.1
+export V=6.0
 
 # Preserve /system/addon.d in /tmp/addon.d
 preserve_addon_d() {