bonding: set correct vlan id for alb xmit path

The commit d3ab3ffd
(bonding: use rlb_client_info->vlan_id instead of ->tag)
remove the rlb_client_info->tag, but occur some issues,
The vlan_get_tag() will return 0 for success and -EINVAL for
error, so the client_info->vlan_id always be set to 0 if the
vlan_get_tag return 0 for success, so the client_info would
never get a correct vlan id.

We should only set the vlan id to 0 when the vlan_get_tag return error.

Fixes: d3ab3ffd

 (bonding: use rlb_client_info->vlan_id instead of ->tag)

CC: Ding Tianhong <dingtianhong@huawei.com>
CC: Jay Vosburgh <fubar@us.ibm.com>
CC: Andy Gospodarek <andy@greyhouse.net>
Signed-off-by: Ding Tianhong <dingtianhong@huawei.com>
Acked-by: Veaceslav Falico <vfalico@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>