Remember whether we sent our key to another node.

In tinc 1.0.x, this was tracked in node->inkey, however in tinc 1.1 we have an abstraction layer for
the legacy cipher and digest, and we don't keep an explicit copy of the key around. We cannot use
cipher_active() or digest_active(), since it is possible to set both to the null algorithm. So add a bit to
node_status_t.

src/net_setup.c

@@ -319,6 +319,8 @@ static void keyexpire_handler(void *data) {
 void regenerate_key(void) {
 	logger(DEBUG_STATUS, LOG_INFO, "Expiring symmetric keys");
 	send_key_changed();
+	for splay_each(node_t, n, node_tree)
+		n->status.validkey_in = false;
 }
 
 /*