tools/btpclient: Add btp disconnect handler

This patch adds btp disconnect handler to btp client.
diff --git a/tools/btpclient.c b/tools/btpclient.c
index 3d9e449..4097c05 100644
--- a/tools/btpclient.c
+++ b/tools/btpclient.c
@@ -2892,6 +2892,12 @@
 	l_main_quit();
 }
 
+static void btp_disconnect_handler(struct btp *btp, void *user_data)
+{
+	l_info("btp disconnected");
+	l_main_quit();
+}
+
 static void client_ready(struct l_dbus_client *client, void *user_data)
 {
 	l_info("D-Bus client ready, connecting BTP");
@@ -2903,6 +2909,8 @@
 		return;
 	}
 
+	btp_set_disconnect_handler(btp, btp_disconnect_handler, NULL, NULL);
+
 	register_core_service();
 
 	btp_send(btp, BTP_CORE_SERVICE, BTP_EV_CORE_READY,