Ignore the scope attribute of exported routes.

I'm not sure what the scope attribute of routes is supposed to mean.
Both ifconfig and ip route appear to add IPv4 routes to directly
connected networks with link scope, and we definitely don't want to
prevent exporting such routes.
For what it's worth, that's also what Quagga does.

kernel_netlink.c

@@ -860,9 +860,6 @@ filter_kernel_routes(struct nlmsghdr *nh, void *data)
     if(rtm->rtm_protocol == RTPROT_BOOT || rtm->rtm_protocol == RTPROT_BABEL)
         return 0;
 
-    if(rtm->rtm_scope >= RT_SCOPE_LINK)
-        return 0;
-
     if(rtm->rtm_src_len != 0)
         return 0;