LU-559 Keep the o_seq unchanged for 1.8 client

LU-559 Keep the o_seq unchanged for 1.8 client

ost_validate_obdo() arbitrarily change the o_seq to 0 for the requests
from 1.8 client, which will make the 1.8 echo client use the 0 group
mistakenly. In fact, I think we needn't do anything special for the 1.8
client here.

Signed-off-by: Niu Yawei <niu@whamcloud.com>
Change-Id: I93cd3bdbf984f8aef0f5b68f5ee8640f31ded337
Reviewed-on: http://review.whamcloud.com/1182
Tested-by: Hudson
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: wangdi <di.wang@whamcloud.com>