far.py: change initial guess for extinction model to 5 which splits the...

far.py: change initial guess for extinction model to 5 which splits the difference between its previous value of 1 and its current value of 10.  We found some offline cases where 10 wasn't so great and 1 wasn't so great online. Hopefully 5 is better. FIXME ditch this scipy routine.

gstlal-inspiral/python/far.py

@@ -758,7 +758,7 @@ WHERE
 			# for non-uniform binning.
 			return numpy.trapz(square_error, x)
 
-		norm, rate_eff, m = optimize.fmin(ssr, (zl.sum() / bg.sum(), zl.sum(), 10.), xtol = 1e-8, ftol = 1e-8, disp = 0)
+		norm, rate_eff, m = optimize.fmin(ssr, (zl.sum() / bg.sum(), zl.sum(), 5.), xtol = 1e-8, ftol = 1e-8, disp = 0)
 
 		# compute survival probability model from best fit
 		survival_probability = mk_survival_probability(rate_eff, m)