LU-604 open non-exist object should return ENOENT

LU-604 open non-exist object should return ENOENT

when call ll_intent_file_open() against non-exist object, we cannot obtain
RPC request refcount after the call, so subsequent operation should not use
such internal RPC request to avoid to access freed memory.

Change-Id: Ic8cd2a7798d2d454cbe5931eb93b92b1a44cca4b
Signed-off-by: Hongchao Zhang<hongchao.zhang@whamcloud.com>
Reviewed-on: http://review.whamcloud.com/1271
Tested-by: Hudson
Reviewed-by: Fan Yong <yong.fan@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Tested-by: Maloo <whamcloud.maloo@gmail.com>