[evlatests] short shallow drops

[Ken Sowinski]

Rick and I attempted to see if not updating the finge rotation parameters
to the L302 would have an effect on the short shallow drops.  The answer
is yes, they do not occur when fringe rotation is disabled.  The inference
from this is that it is related to something the MIB does when a new
command is received.  Since the MIB updates DDS chirp parameters
periodically whether commands are received or not it seems that MIB-DDS
communications are not the culprit here.  A reasonable hypothesis is
that there is a calculation or timing error such that the DDS is
misprogrammed whenever a new command is processed.