fix bug where horizon factor is stored only for 1 ifo instead of individual ifos

• Prior to the MR, gstlal_inspiral_create_prior_diststats stored horizon factors for only the last SVD file that was given as an option to --svd-file.
  • This MR fixes gstlal_inspiral_create_prior_diststats such that multiple SVD files can be given properly, and so that horizon factors are stored for each of the SVD files (assuming SVD files of different ifos for the same SVD bin are given).
  • The horizon factors are stored as a dictionary with the ifo as keys.
• Prior to the MR, gstlal_inspiral stored the horizon factors from SVD files, and passed them into rankingstat.
  • However, gstlal_inspiral does not evaluate likelihood ratios in offline runs, and reads in horizon factors from prior dist stats in online runs, so gstlal_inspiral does not need horizon factors.
  • This MR removes horizon factor-related lines in gstlal_inspiral, other than assigning None when passing horizon factors to rankingstat.numerator. Downstream when dist stats files are marginalized, horizon factors will be taken from the prior dist stats files when the dist stats files (output of gstlal_inspiral) have None as values for horizon factors.
• inspiral_lr.py is fixed such that a dictionary of horizon factors with ifo names as keys can be processed.
• A bns small dag has been run to test that this MR does not result in job failures.