Async do not clear previous data if entry is different than device name

Bug report

Reported by @appel_c during test at Pollux BL with panda box.

Summary

Here with new scan id the curve f"{device}-{device}" is cleared however should be f"{device}-{entry}".

    @Slot(str)
    def setup_async(self, device: str):
        self.bec_dispatcher.disconnect_slot(
            self.on_async_readback, MessageEndpoints.device_async_readback(self.old_scan_id, device)
        )
        try:
            self._curves_data["async"][f"{device}-{device}"].clear_data()
        except KeyError:
            pass
        if len(self._curves_data["async"]) > 0:
            self.bec_dispatcher.connect_slot(
                self.on_async_readback,
                MessageEndpoints.device_async_readback(self.scan_id, device),
                from_start=True,
            )