staging: lustre: fid: do open-by-fid by default

Currently client open-by-fid often packs name into the request,
but the name may be invalid, eg. NFS export, and even if it's
valid, it may cause inconsistency because this operation is done
on this fid, which is globally unique, but name not.

Since open-by-fid doesn't pack name, for striped dir we can't know
parent stripe fid on client, so we set parent fid the same as
child fid, and MDT has to find its parent fid from linkea (this is
already supported by MDT).

M_CHECK_STALE becomes obsolete.

Unset MDS_OPEN_FL_INTERNAL from open syscall flags, because these
flags are internally used, and should not be set from user space.

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>
Intel-bug-id: https://jira.hpdd.intel.com/browse/LU-3544
Reviewed-on: http://review.whamcloud.com/7476
Reviewed-on: http://review.whamcloud.com/10692


Reviewed-by: Fan Yong <fan.yong@intel.com>
Reviewed-by: Nathaniel Clark <nathaniel.l.clark@intel.com>
Reviewed-by: wangdi <di.wang@intel.com>
Reviewed-by: John L. Hammond <john.hammond@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>
Signed-off-by: James Simmons <jsimmons@infradead.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>