Fix for #3674 Can't `rm` containers when disk full

Rather than creating a new directory and moving it there before
deleting that new directory, just move the directory we intend to
delete.

In the old way, the Mkdirall could fail, which meant that you
couldn't delete containers when the disk was full.

Tested.

Docker-DCO-1.1-Signed-off-by: Peter Waller <p@pwaller.net> (github: pwaller)