Update global_enkf ctest for tapering of perturbations

[CatherineThomas-NOAA]

The global_enkf ctest needs to be updated to include a change to the configuration of GFSv17. The upper layer ensemble spread is too large, so we are enabling a new feature in the EnKF to reduce the spread as part of the ensemble analysis (Issue #728).

This feature is being turned on in the global-workflow through PR#3097. The GSI repo EnKF test need to be updated to match.