fix filesystem walk path

[liuxu623]

fix #3058

[GordonTheTurtle]

Please sign your commits following these rules:
https://github.com/moby/moby/blob/master/CONTRIBUTING.md#sign-your-work
The easiest way to do this is to amend the last commit:

$ git clone -b "fix-filesystem-walk-path" git@github.com:liuxu623/distribution.git somewhere
$ cd somewhere
$ git commit --amend -s --no-edit
$ git push -f

Amending updates the existing PR. You DO NOT need to open a new one.

[codecov]

Codecov Report

Merging #3059 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #3059   +/-   ##
=======================================
  Coverage   60.73%   60.73%           
=======================================
  Files         102      102           
  Lines        8073     8073           
=======================================
  Hits         4903     4903           
  Misses       2518     2518           
  Partials      652      652

Flag	Coverage Δ
#linux	60.73% <ø> (ø)	⬆️

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[milosgajdos]

@liuxu623 can you rebase

[milosgajdos]

ping @liuxu623