le_audio: Stop audio on shutdown

SupprNoisy was set to true if the previously active out device was still
connected. In case of system shutdown it was still connected. The
LeAudioStateMachine only disconnected the device after ~10ms.

Bug: 275670791
Test: manual
Tag: #feature
Change-Id: Iadfa4ffbbc581c122b6f822aa1d3fc907059d08a