Serial slave doesn't close serial port

[rfporter]

The VISA session of the Serial slave is often left open even though shutdown was called.

This is due to the serial daemon performing a VISA read while VISA close is called. The VISA session is held open by the VISA read.

To fix this, VISA close should be called within the Serial Daemon during shutdown.

[rfporter]

[rfporter]

Workaround: call VISA close on the serial port 11 seconds after calling shutdown.