Disable Le Audio communication flag before notifying audio lost

While disconnecting BT LE audio headset, currently audio lost is notified
and then mLeAudioSetAsCommunicationDevice is cleared. This is causing
wrong AudioState because BlueToothRouteManager sees that BT LE audio
is still connected. So first clear the flag and notify audio lost
so that when BlueToothRouteManager queries BT connected state,
LE audio devices are ignored and moves to AudioOff state.

Bug: 237642330
Change-Id: Id6b76a84e557a1a74511224fc7d0e3e336262982