Fix handling of existing remapped ice-shelf melt

Since the step in the init test case doesn't exist at construciton
of the associated step in files_for_e3sm, we need to add the link
to the output file during `setup()` instead.

compass/ocean/tests/global_ocean/files_for_e3sm/remap_ice_shelf_melt.py

@@ -30,34 +30,40 @@ def __init__(self, test_case, init):
 
         init : compass.ocean.tests.global_ocean.init.Init
             The test case that produces the initial condition for this run
-        """  # noqa: E501
+        """
         super().__init__(test_case, name='remap_ice_shelf_melt', ntasks=512,
                          min_tasks=1)
         self.init = init
+
+    def setup(self):
+        """
+        setup input files based on config options
+        """
+        super().setup()
+        if not self.with_ice_shelf_cavities:
+            return
+
         filename = 'prescribed_ismf_paolo2023.nc'
-        if init is None:
+
+        if self.init is None:
             self.add_input_file(
                 filename='Paolo_2023_ANT_G1920V01_IceShelfMelt.nc',
                 target='Paolo_2023_ANT_G1920V01_IceShelfMelt.nc',
                 database='initial_condition_database',
                 url='https://its-live-data.s3.amazonaws.com/height_change/Antarctica/Floating/ANT_G1920V01_IceShelfMelt.nc')    # noqa: E501
-        elif 'remap_ice_shelf_melt' in self.init.steps:
+            self.add_output_file(filename=filename)
+        else:
+            if 'remap_ice_shelf_melt' not in self.init.steps:
+                raise ValueError('Something seems to be misconfigured. No '
+                                 'remap_ice_shelf_melt step found in init '
+                                 'test case.')
             melt_path = \
                 self.init.steps['remap_ice_shelf_melt'].path
 
             self.add_input_file(
                 filename=filename,
                 work_dir_target=f'{melt_path}/{filename}')
 
-    def setup(self):
-        """
-        setup input files based on config options
-        """
-        super().setup()
-        filename = 'prescribed_ismf_paolo2023.nc'
-        if self.with_ice_shelf_cavities:
-            self.add_output_file(filename=filename)
-
     def run(self):
         """
         Run this step of the test case