uid/gid of the builder should not leak in the aci #16
Description
After copying all necessary files in a temporary directory, goaci creates the tar archive with the following code:
err = filepath.Walk(acidir, aci.BuildWalker(acidir, iw))
aci.BuildWalker adds files in the tarball and preserves the uid/gid of the files. I am testing goaci as user alban and uid 1000 so the files copied by goaci in the temporary directory belong to 1000 and in files in the tar archive belong to 1000 (see populateHeaderUnix).
This goes against #10. I think we should just mark all files as belonging to root in the tar file. We can revisit this when appc/spec#231 gets fixed.
It might be possible to mark all files as belonging to root without patching aci.BuildWalker by adding an intermediary function call between Walk and BuildWalker which will provide a custom os.FileInfo.
(Issue discovered while reviewing #13)