[evlatests] slow attenuator setting on ea16 IF D

[Doug Whiton]

> I would consider a sticky subreflector that moves a little further
> each time it is commanded until it finally gets there.
>

I witnessed this just last Friday.  I noticed that Ants. 11, 12, 13, 16
and 27 were having difficulty settling into position.  They would move to
within a few counts on either side of the intended position, waiting about
15-20 seconds between each try, then overshoot to the other side.  I
talked with Wayne about this.  He said that a firmware change and possibly
a hardware change would be necessary if we wanted to fix this.

Doug