LU-7716 mdt: No is_subdir check for same dir rename

LU-7716 mdt: No is_subdir check for same dir rename

In rename, if the source and target are in the same
directory, then it does not need is_subdir check.

Signed-off-by: Di Wang <di.wang@intel.com>
Change-Id: I03a4aff71b2c284197a8f78f6306568249162aca
Reviewed-on: http://review.whamcloud.com/18172
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Lai Siyao <lai.siyao@intel.com>
Reviewed-by: Jinshan Xiong <jinshan.xiong@intel.com>
Reviewed-by: John L. Hammond <john.hammond@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>