Fix memory leaks in route(8).

Submitted by:	Tom Rix (trix_juniper.net)
MFC after:	2 weeks
Differential Revision:	https://reviews.freebsd.org/D9676

sbin/route/route.c

@@ -523,6 +523,7 @@ flushroutes_fib(int fib)
 			printf("done\n");
 		}
 	}
+	free(buf);
 	return (error);
 }
 
@@ -1439,6 +1440,7 @@ interfaces(void)
 		rtm = (struct rt_msghdr *)(void *)next;
 		print_rtmsg(rtm, rtm->rtm_msglen);
 	}
+	free(buf);
 }
 
 static void