Add missing is_loaded() method on directory's interface

It is not supercritical, but it is nice to have.

Change-Id: Iaf6c6c8d06ab1ea120da6957a5b3b6f1758f8550

neutron_lib/plugins/directory.py

@@ -90,3 +90,7 @@ def get_plugins():
 
 def get_unique_plugins():
     return _get_plugin_directory().unique_plugins
+
+
+def is_loaded():
+    return _get_plugin_directory().is_loaded

neutron_lib/tests/unit/plugins/test_directory.py

@@ -59,6 +59,11 @@ class DirectoryTestCase(base.BaseTestCase):
         directory.add_plugin('foo2', fake_plugin)
         self.assertEqual(1, len(directory.get_unique_plugins()))
 
+    def test_is_loaded(self):
+        self.assertFalse(directory.is_loaded())
+        directory.add_plugin('foo1', fake_plugin)
+        self.assertTrue(directory.is_loaded())
+
 
 class PluginDirectoryTestCase(base.BaseTestCase):
 

releasenotes/notes/add-directory-is-loaded-e9da5b65824dddad.yaml

@@ -0,0 +1,5 @@
+---
+features:
+  - |
+    Introduced neutron_lib.plugins.directory.is_loaded(). This can be used
+    in lieu of len(plugins()) or bool(plugins()) or plugins() alone.