Fixed handler destructor and memleak.

Handler destructor was called only if handler was brought down
while the server was running. Also it didn't free the context struct.

Change-Id: I8e71f4abc2bb314528416eeba063b48f2fb79773

src/knot/server/server.c

@@ -386,11 +386,14 @@ int server_free_handler(iohandler_t *h)
 	if (!h || !h->server) return KNOT_EINVAL;
 	if (h->server->state & ServerRunning) {
 		dt_stop(h->unit);
-		if (h->dtor) h->dtor(h);
 		dt_join(h->unit);
 	}
 
 	/* Destroy dispatcher and worker */
+	if (h->dtor) {
+		h->dtor(h->data);
+		h->data = NULL;
+	}
 	dt_delete(&h->unit);
 	free(h->state);
 	memset(h, 0, sizeof(iohandler_t));

src/knot/server/udp-handler.c

@@ -515,6 +515,7 @@ void udp_free_ctx(void *ctx)
 	for (unsigned i = 0; i < _ctx->rqlen; ++i) {
 		_udp_deinit(_ctx->rqs[i]);
 	}
+	free(_ctx);
 }
 
 int udp_writer(iohandler_t *h, dthread_t *thread)