usertests: Fix subdir and rename tests
usertests: Fix subdir and rename tests

These both tried to create a directory called 'dd', but that's a binary
now.  Rename to 'sub'.

bowlofstew/sv6,bowlofstew/sv6,bowlofstew/sv6,aclements/sv6,aclements/sv6,aclements/sv6,aclements/sv6,bowlofstew/sv6,bowlofstew/sv6,aclements/sv6