Rfcomm Test: RFCOMM socket should be disconnected in BLE_ON mode

In BT disabled state under BLE_ON mode, it's impossible to determine the device's connection status. Determine whether the RFCOMM Socket or ACL link has been disconnected based on successful data transmission.

Change-Id: I14fa8ac368a2750df0475a0f77f7675cbaa89d9b
Test: atest BumbleBluetoothTests:RfcommTest#clientRfcommDeviceDisconnectedOnBleOnMode
Bug: 110362576
Bug: 387198958
Flag: com.android.bluetooth.flags.disconnect_acls_by_bredr_disabled