mm-netlink: use unaligned netlink attribute length

Alignment padding is not accounted for in the netlink attribute
length.  Fix to avoid warnings later if we add shorter fixed
length attributes, even though it currently makes no difference
since we only add a 4 byte attribute

Signed-off-by: Bjørn Mork <bjorn@mork.no>

src/mm-netlink.c

@@ -98,7 +98,7 @@ append_netlink_attribute (NetlinkMessage *msg,
     memset ((char *) msg->data + old_len, 0, msg->len - old_len);
 
     new_attr.rta_type = type;
-    new_attr.rta_len = attr_len;
+    new_attr.rta_len = RTA_LENGTH (len);
     next_attr_abs_pos = (char *) msg->data + next_attr_rel_pos;
     memcpy (next_attr_abs_pos, &new_attr, sizeof (struct rtattr));