minor cleanup to backup/restore scripts for devices

tools/backup_sdcard

@@ -17,6 +17,7 @@ read
 sudo umount $device?
 sudo umount $device
 
+sudo sync
 sudo pv -tpreb $device | dd bs=4M | pixz > $dest_file
 sudo sync
 

tools/restore_sdcard

@@ -12,7 +12,6 @@ if [[ ! -f $source_file ]]; then
 fi
 
 device=$2
-timestamp=`date +%Y%m%d`
 
 echo "about to restore $source_file onto $device"
 echo "ctrl-c or [enter]"