When the sink goes from PLAYING to READY and then back to PLAYING, the initialization of the audioclient in prepare() fails with the error AUDCLNT_E_ALREADY_INITIALIZED. As a result, the playback stops. To fix this, we need to drop the AudioClient in unprepare() and grab a new one in prepare() to be able to initialize it again with the new buffer spec. Part-of: <https://gitlab.freedesktop.org/gstreamer/gst-plugins-bad/-/merge_requests/2096>