Fix netcdf format and engine definitions

Fix netcdf format and engine definitions, which for some reason
need to be called as mpas_tools.io.default_engine rather than
using: from mpas_tools.io import default_engine. The latter approach
returned a None type variable, which threw an error when passed to
compute_mpas_region_masks.

compass/landice/mesh.py

@@ -1,10 +1,11 @@
 import time
 
 import jigsawpy
+import mpas_tools.io
 import numpy as np
 import xarray
 from geometric_features import FeatureCollection, GeometricFeatures
-from mpas_tools.io import default_format, write_netcdf
+from mpas_tools.io import write_netcdf
 from mpas_tools.logging import check_call
 from mpas_tools.mesh.conversion import convert, cull
 from mpas_tools.mesh.creation import build_planar_mesh
@@ -653,5 +654,6 @@ def make_region_masks(self, mesh_filename, mask_filename, cores, tags):
             '-o', mask_filename,
             '-t', 'cell',
             '--process_count', f'{cores}',
-            '--format', default_format]
+            '--format', mpas_tools.io.default_format,
+            '--engine', mpas_tools.io.default_engine]
     check_call(args, logger=logger)