Add the ability to delete the old_root
Add the ability to delete the old_root

The function "littleDoctor" will delete all files in old_root and will
not dip into different file systems.

hugelgupf/u-root,GanShun/u-root,u-root/u-root,hugelgupf/u-root,rminnich/u-root,GanShun/u-root,hugelgupf/u-root,u-root/u-root,rminnich/u-root,rminnich/u-root,u-root/u-root,GanShun/u-root,hugelgupf/u-root,rminnich/u-root