Ignore routes in non-main tables

Route lookup in Linux is bounded by `ip rules` as well
as the contents of specific routing tables.  With the
advent of vrf's(l3mdev's) non-default tables are regularly being
used for routing purposes.

dnsmasq listens to all route changes on the box and responds
to each one with an event.  This is *expensive* when a full
BGP routing table is placed into the linux kernel, moreso
when dnsmasq is responding to events in tables that it will
never actually need to respond to, since dnsmasq at this
point in time has no concept of vrf's and would need
to be programmed to understand them.  Help alleviate this load
by reducing the set of data that dnsmasq pays attention to
when we know there are events that are not useful at this
point in time.

Signed-off-by: Donald Sharp <donaldsharp72@gmail.com>

src/netlink.c

@@ -360,7 +360,9 @@ static void nl_async(struct nlmsghdr *h)
 	 failing. */ 
       struct rtmsg *rtm = NLMSG_DATA(h);
       
-      if (rtm->rtm_type == RTN_UNICAST && rtm->rtm_scope == RT_SCOPE_LINK)
+      if (rtm->rtm_type == RTN_UNICAST && rtm->rtm_scope == RT_SCOPE_LINK &&
+	  (rtm->rtm_table == RT_TABLE_MAIN ||
+	   rtm->rtm_table == RT_TABLE_LOCAL))
 	queue_event(EVENT_NEWROUTE);
     }
   else if (h->nlmsg_type == RTM_NEWADDR || h->nlmsg_type == RTM_DELADDR)