client: Fix stat of relative symlinks

client: Fix stat of relative symlinks

Stat of symlinks that are relative to their location
would return -ENOENT because the symlink target is
being appended to the path rather than replacing it.
This fix replaces the symlink component with the path
of the symlink target (in the case that its a relative
symlink), and avoids updating the inode to point the
symlink (keeps at the parent).

Signed-off-by: Sam Lang <sam.lang@inktank.com>