fileutil: Do not use os.Link in CopyFile
fileutil: Do not use os.Link in CopyFile

This is rather confusing since hardlink is not the same thing as a regular copy.
It is actually breaking some other code, that is why this is being changed.

Change-Id: 4b71f60415
Story-Id: salsaflow/salsaflow#125

salsaflow/salsaflow,salsaflow/salsaflow