Fixed a bug in forgetfs.
Fixed a bug in forgetfs.

This manifested as ForgetFSTest.MkDir pacicking now and then in a manner
like this:

    https://gist.githubusercontent.com/jacobsa/2d12150beca1043f71b0/raw/28e0a01a9276799ad820970a05b522367222c331/gistfile1.txt

jacobsa/fuse,clekstro/fuse