support batching of ip route get commands

This patch replaces exits with returns in
ip route get command handling. This allows batching
of ip route get commands.

$cat route_get_batch.txt
route get 10.0.14.2
route get 12.0.14.2
route get 10.0.14.4

$ip -batch route_get_batch.txt
local 10.0.14.2 dev lo  src 10.0.14.2
    cache <local>
12.0.14.2 via 192.168.0.2 dev eth0  src 192.168.0.15
    cache
10.0.14.4 dev dummy0  src 10.0.14.2
    cache
Signed-off-by: Roopa Prabhu <roopa@cumulusnetworks.com>

ip/iproute.c

@@ -1682,15 +1682,15 @@ static int iproute_get(int argc, char **argv)
 		req.n.nlmsg_type = RTM_GETROUTE;
 
 		if (rtnl_talk(&rth, &req.n, &req.n, sizeof(req)) < 0)
-			exit(2);
+			return -2;
 	}
 
 	if (print_route(NULL, &req.n, (void*)stdout) < 0) {
 		fprintf(stderr, "An error :-)\n");
-		exit(1);
+		return -1;
 	}
 
-	exit(0);
+	return 0;
 }
 
 static int restore_handler(const struct sockaddr_nl *nl,