Invert logic

src/freedombone-backup-local

 function remove_backup_directory {
     if [ $1 ]; then
         if [[ $1 == "remove" ]]; then
-            if [ ! -d $USB_MOUNT/backup ]; then
+            if [ -d $USB_MOUNT/backup ]; then
                 rm -rf $USB_MOUNT/backup
                 echo $'Existing backup directory removed'
                 unmount_drive