backuptool: only restore from same major.minor version

Change-Id: I63113fa9b3cbc6b0e1b3df75ef7dfb3160ee5062

prebuilt/common/bin/backuptool.functions

@@ -5,7 +5,7 @@
 
 export C=/tmp/backupdir
 export S=/system
-export V=9
+export V=10.1
 
 backup_file() {
   if [ -e "$1" ]; then

prebuilt/common/bin/backuptool.sh

@@ -5,7 +5,7 @@
 
 export C=/tmp/backupdir
 export S=/system
-export V=10
+export V=10.1
 
 # Preserve /system/addon.d in /tmp/addon.d
 preserve_addon_d() {
@@ -20,10 +20,10 @@ restore_addon_d() {
   rm -rf /tmp/addon.d/
 }
 
-# Proceed only if /system is the expected major version
+# Proceed only if /system is the expected major and minor version
 check_prereq() {
 if ( ! grep -q "^ro.cm.version=$V.*" /system/build.prop ); then
-  echo "Not backing up files from incompatible version."
+  echo "Not backing up files from incompatible version: $V"
   exit 127
 fi
 }