LU-3544 nfs: don't store parent fid

LU-3544 nfs: don't store parent fid

It's not necessary to store parent fid in lli_pfid, because MDT
can get it's parent fid from linkea, and now that DNE stripe
directory stores master inode fid in lli_pfid, stop storing parent
fid to avoid conflict.

Signed-off-by: Lai Siyao <lai.siyao@intel.com>
Change-Id: I924c29a1d58b008026d37265978c81ca1aa21ebb
Reviewed-on: http://review.whamcloud.com/10692
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Fan Yong <fan.yong@intel.com>
Reviewed-by: wangdi <di.wang@intel.com>
Reviewed-by: Nathaniel Clark <nathaniel.l.clark@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>