staging: lustre: fid: add a connect flag for open by FID

Add OBD_CONNECT_OPEN_BY_FID for open by FID, if MDS supports this,
for open by FID, it won't retry with name if object with the FID
doesn't exist; while if client supports this, client won't pack
name in open request if FID is known.

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/8093


Reviewed-by: John L. Hammond <john.hammond@intel.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Signed-off-by: James Simmons <jsimmons@infradead.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>