Reset auto IDs in multigroup conversion test

Reset auto IDs before creating material in the test.

Author: GuySten

tests/unit_tests/dagmc/test_convert_to_multigroup.py

@@ -15,7 +15,8 @@
 def test_convert_to_multigroup_without_particles_batches(run_in_tmpdir):
     """Test that convert_to_multigroup works with DAGMC model without
     setting particles/batches beforehand."""
-
+    openmc.reset_auto_ids()
+    
     mat = openmc.Material(name="mat")
     mat.add_nuclide("Fe56", 1.0)
     mat.set_density("g/cm3", 7.0)