gstlal_inspiral_calc_likelihood, gstlal_inspiral_calc_rank_pdfs,
gstlal_inspiral_marginalize_likelihood, and gstlal_inspiral_plot_background.
This option sets the zero_lag_in_background flag in the
ThincaCoincParamsDistributions instances to true so that zerolag rates are
added to background rates before calculating the coincident paramater PDFs