[evlatests] Zeros in Friday data

[Rick Perley]

    I noted in my earlier report that something like 7% of the data were 
noted as integer zeros, but I had not identified their origin.  A few 
minutes extra poking around revealed where they are -- it is I think 
much the same situated reported by Vivek.

    The zero pattern is quite regular, and quite odd: 
   
Subband 1 (spectral window 0) is the only one with extra zeros.
Within this window, for the entire length of the run:
        Antennas 3 and 4 (all polarization products) are zeroed with all 
other antennas except 1.
       Antennas 9 and 11 are zeroed with all others except antennas 1, 
2, and 7
       Antennas 14 and 15 are zeroed with all others except antennas 1 2 
7 8 and 12
       Antennas 18 and 19 are zeroed with all others except antennas 1 2 
7 8 12 13 and 16.