Fix for systemtest test_korzhnev_2005_all_data_disp_speed_bug.
The precision is lowered, and now matches the original systemtest.
Task #7807 (https://gna.org/task/index.php?7807): Speed-up of dispersion models for Clustered analysis.
Authored by: tlinnet 2014-06-17
Parent: [r24022]
Child: [r24024]
