Fix non-determinism in single IFO FAR output

There's a new issue with some of our single IFO FAR columns.
far_sngl_H1, far_sngl_L1, and far_sngl_V1 are meant to be calculated as far_factor * Max(far_2h_sngl, far_1d_sngl, far_1w_sngl)
See postcoh_finalsink.py
(far_factor is a command line argument, and is typically 2)

Printing the zerolags, this calculation works most of the time, but sometimes appears random. far_sngl_H1 is sometimes up to 100x the correct value. It's usually within an order of magnitude, so it may be that the wrong trigger's FAR is being output (or that we're using uninitialized memory or another float field). I thought that maybe it was getting it from the wrong IFO, but none of the other IFOs would have given the same results.

@andrewmichael.gozzard has performed a git bisect, and the issue only occurs after !27 (merged), d6325e73
That commit only set the field to be output, but an earlier commit caused it to stop displaying at all (I believe it was !25 (403fe6be), but I need to double check)

This is different to #11, as it wasn't a preexisting issue, and should be fixed separately.