Fix backup script derp

Change-Id: I9b0bb774ff645239f26d243a55f4414defebf22c
diff --git a/prebuilt/common/bin/backuptool.sh b/prebuilt/common/bin/backuptool.sh
index ecda592..07a5467 100755
--- a/prebuilt/common/bin/backuptool.sh
+++ b/prebuilt/common/bin/backuptool.sh
@@ -33,7 +33,7 @@
 if [ ! -r /system/build.prop ]; then
     return 0
 fi
-if ( ! grep -q "^ro.bliss.version=$V.*" /system/build.prop ); then
+if ( ! grep -q "^ro.bliss.display.version=$V.*" /system/build.prop ); then
   echo "Not backing up files from incompatible version: $V"
   return 0
 fi