ansible-test - Fix plugin loading.

This fixes a traceback when loading plugins that use dataclasses.

changelogs/fragments/ansible-test-plugin-loading.yml

@@ -0,0 +1,2 @@
+bugfixes:
+  - ansible-test - Fix plugin loading.

test/lib/ansible_test/_internal/util.py

@@ -770,11 +770,10 @@ def load_module(path, name):  # type: (str, str) -> None
 
     spec = importlib.util.spec_from_file_location(name, path)
     module = importlib.util.module_from_spec(spec)
+    sys.modules[name] = module
     # noinspection PyUnresolvedReferences
     spec.loader.exec_module(module)
 
-    sys.modules[name] = module
-
 
 def sanitize_host_name(name):
     """Return a sanitized version of the given name, suitable for use as a hostname."""