Couple the DCM/BPM closed loop to shutter status

[canismarko]

From Vincent:

What would be useful though is a while loop checking the shutter
status. If the A or B shutter are closed, one should stop the DCM /
BPM closed loop (overnight beam dump for instance).

I'm thinking monitoring the shutter status by using the pyepics callbacks and enabling/disabling the closed loop that way.

[prjemian]

This might be over-cautious (like wearing both a belt and suspenders). Most of the closed loop BPM controls in EPICS have allowance for signals going out of range such as a beam dump. Verify with @kmpeters for 32-ID or @Engbretson for 2-BM. The control system is supposed to take care of this.

[canismarko]

Good to know. Vincent is following up on it.