floss: SCO: Avoid use after free

The unique_ptr<tUIPC_STATE> sco_uipc could be overwritten without
calling UIPC_Close, this could leave the UIPC thread alive and access
the UIPC structure while is already freed.

Bug: 373228946
Tag: #floss
Test: mmm packages/modules/Bluetooth
Test: bluetooth_AdapterAUHealth.all_floss
Flag: EXEMPT, Floss-only change
Change-Id: I085e70db774310118b9b7a2e9a4325c41ed71900