[evlatests] Tests April 21

[Barry Clark]

Turns out that the problem with antenna 18 is that its L302 was not
phase switching at all.  When I told the correlator not to expect it
to switch, the A side came through nicely.  The C side is down by a
largish factor.  As I said yesterday, I suspect this is a problem
with contamination somewhere - neither the total or switched power
go away when I put a lot of attenuation in the T304.

Fired up a pointing run on general principles.  Had to reboot two 
L302s to make them lock, 13 BD and 16 AC.