drivers/nemo_concepts: let 'ktherm=-1' only disable thermodynamics

When CICE learned to disable the thermodynamics in 83686a3 (Implement
box model test from 2001 JCP paper (CICE-Consortium#151), 2018-10-22), it was not
envisioned that this capability would be used with 'calc_strair =
.true.'. This currently does not work (the atmospheric stresses are
always zero). This is because they are computed in
'icepack_atmo::icepack_atm_boundary', called from
'icepack_therm_vertical::icepack_step_therm1', itself called from
'ice_step_mod::step_therm1', a call which is skipped if thermodynamics
is disabled ('ktherm<0').

Adjust the logic in ice_step to always call 'step_therm1', and update
Icepack to a commit in which some parts of the computation in
'icepack_step_therm1' are only done if 'ktherm >= 0', while others
(namely the computation of the atmospheric stresses) are always done.

cicecore/drivers/direct/nemo_concepts/CICE_RunMod.F90

@@ -215,22 +215,20 @@ subroutine ice_step
          !$OMP PARALLEL DO PRIVATE(iblk)
          do iblk = 1, nblocks
 
-            if (ktherm >= 0) then
-
       !-----------------------------------------------------------------
       ! Scale radiation fields
       !-----------------------------------------------------------------
 
-               if (calc_Tsfc) call prep_radiation (iblk)
+            if (calc_Tsfc .and. ktherm >= 0) call prep_radiation (iblk)
 
       !-----------------------------------------------------------------
       ! thermodynamics and biogeochemistry
       !-----------------------------------------------------------------
 
-               call step_therm1     (dt, iblk) ! vertical thermodynamics
+            call step_therm1     (dt, iblk) ! vertical thermodynamics
+            if (ktherm >= 0) then
                call biogeochemistry (dt, iblk) ! biogeochemistry
                call step_therm2     (dt, iblk) ! ice thickness distribution thermo
-
             endif
 
          enddo ! iblk