Critical fixes for systemtest: Relax_disp.test_hansen_cpmg_data_missing_auto_analysis.
task #7793: (https://gna.org/task/?7793) Speed-up of dispersion models.
This was found necessary after commit 23216.
It is suspected that when relax have touched boundary values which made
math domain errors, the error cathing have created local minima or
interfered with the simplex search algorithm.
