search_thresh_fftw image peak calc not right when nant<27

[caseyjlaw]

When providing mock metadata with 20 antennas, some tests fail. The test_seg.py logging shows that the state method for finding a peak pixel is finding weirdness in the input image. Something probably wrong in the structure of the data passed in to this function.

state.py                   646 WARNING  More than one peak pixel ([ 0  0  0 ... 31 31 31], [ 0  1  2 ... 29 30 31]). Using first.
state.py                   646 WARNING  More than one peak pixel ([ 0  0  0 ... 31 31 31], [ 0  1  2 ... 29 30 31]). Using first.