Return codes from namelist reads are not always checked

[nichannah]

For example there is code like:

ierr = check_nml_error(io_status,'ocean_vert_kpp_mom4p1_nml')

and

ierr = check_nml_error(io_status,'ocean_vert_kpp_mom4p1_nml')

but no following check that ierr does not indicate an error. This means that a typo within a namelist would result in default parameters being silently used. Model output will be incorrect without the user knowing.