LU-6166 utils: fix bug in lr_link

LU-6166 utils: fix bug in lr_link

When create a hard link of a file, the path and the file name are
same if it at the root directory, so the length of the path and name
will be the same in this case.

Signed-off-by: Wu Libin <lwu@ddn.com>
Change-Id: I3a72491efdc041ad0e96d036b04600b76bb646fe
Reviewed-on: http://review.whamcloud.com/13546
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Yang Sheng <yang.sheng@intel.com>
Reviewed-by: Dmitry Eremin <dmitry.eremin@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>