ice_init: do broadcast 'default_season'

When the 'default_season' namelist setting was added in 01494c7 (Nml
settings (CICE-Consortium#208), 2018-10-19) to replace 'l_winter' and 'l_spring', a
call to 'broadcast_scalar' was forgotten, such that the 'default_season'
value from the namelist is only use on the first MPI process; all other
processes get the hardcoded default value 'winter' defined in
'ice_init::input_data', resulting in different initialization across the
grid for several variables if anything other than 'winter' is used in
the namelist.

Fix that by broadcasting 'default_season' to all MPI procs.

cicecore/cicedynB/general/ice_init.F90

@@ -906,6 +906,7 @@ subroutine input_data
       call broadcast_scalar(albsnowi,             master_task)
       call broadcast_scalar(ahmax,                master_task)
       call broadcast_scalar(atmbndy,              master_task)
+      call broadcast_scalar(default_season,       master_task)
       call broadcast_scalar(fyear_init,           master_task)
       call broadcast_scalar(ycycle,               master_task)
       call broadcast_scalar(atm_data_format,      master_task)