MuSR: Kepco Protocol no reply within 2000ms error [Timebox: 0,5 day]

At 9:51AM on monday the 22nd of february Peter Baker reported that the kepco responsible for the Z axis of the zero field controller on MuSR was failing to write, looking at the IOC logs this happened:
`[2021-02-22 09:51:19] 2021/02/22 09:51:19.199521 L0 IN:MUSR:KEPCO_03:OUTPUTMODE: No reply within 2000 ms to "FUNC:MODE?ESC[7m<0d>ESC[27mESC[7m<0a>ESC[27m"`

This happened for about 10 minutes, we weren't sure if it was just a network error so left it for the time being.
`0xd` and `0xa` are the carriage return and line feed characters which we would expect but there are some other weird characters that we don't.

### Acceptance Criteria:
- The source of the error is understood
- The error is either fixed or spun out into a new ticket

Non sono indicati file sorgente né test. Inizia dalla voce del log IOC per IN:MUSR:KEPCO_03:OUTPUTMODE e traccia la comunicazione del protocollo Kepco per il controller di campo nullo dell’asse Z. Il lavoro è completato quando la causa del timeout di 2000 ms e dei caratteri imprevisti è stata compresa, quindi risolta o suddivisa in un nuovo ticket.

Scritto dal modello di indicizzazione a partire dal testo della issue.