FAULT_BUSY
try_delete_key("closed socket, delete current key", sk, 100, 100, 0, -1, -1, FAULT_BUSY);
try_delete_key("closed socket, delete rnext key", sk, 200, 200, 0, -1, -1, FAULT_BUSY);
try_delete_key("closed socket, delete current+rnext key", sk, 200, 200, 0, -1, -1, FAULT_BUSY);