Pipewire backend: Early pw_deinit() called cause Segfault

Reproduce: ``` use rodio::{DeviceSinkBuilder}; #[tokio::test] async fn test_output() { let out = DeviceSinkBuilder::open_default_sink().unwrap(); let out2 = DeviceSinkBuilder::open_default_sink().unwrap(); drop(out); drop(out2); } ``` with pipewire feature enabled.