This testdef is used to test a stealth feature in mpaso introduced by
PR #2726. It changes one mpaso namelist variable,
    config_land_ice_flux_mode
from its default value to 'coupled'.
This tests the ocn/glcshelf coupling.

It also specified that DATM forcing should be restricted to 1958.
This allows JRA1p5 forcing to be used without a large input data requirement.
