With `fs.RootPath`, the target file will be the file which the softlink
points to, like:
touch /tmp/zzz
ln -s /tmp/zzz /tmp/xxx
ln /tmp/xxx /tmp/yyy
The `/tmp/yyy` should be same with the `/tmp/xxx`, not `/tmp/zzz`. We
should allow hardlink to softlink file.
Signed-off-by: Wei Fu <fhfuwei@163.com>