AudioService: fix BT SCO audio starting from system server

When a request to use Bluetooth SCO for calls comes from the system
UID, it means this request is from Telecom package and should not
trigger calls to startScoUsingVirtualVoiceCall().

Flag: EXEMPT bug fix
Test: repor steps in bug
Bug: 366363233
Change-Id: I0c7a71fe2b24b3cf995f02f53d15836e3f2974eb