Fix collection syncing when creating new collections from the outliner

We were not passing a scene collection parent to the BKE_collection_add
function, which in turn made syncing not work.

Right now we:
* Explicitly pass the master collection in this case
* Fallback to the master collection in other cases

With unittest.

tests/python/view_layer/CMakeLists.txt

@@ -62,6 +62,7 @@ endmacro()
 
 VIEW_LAYER_TEST(active_collection)
 VIEW_LAYER_TEST(background_set)
+VIEW_LAYER_TEST(collection_new_sync)
 VIEW_LAYER_TEST(collection_rename_a)
 VIEW_LAYER_TEST(collection_rename_b)
 VIEW_LAYER_TEST(evaluation_render_settings_a)

tests/python/view_layer/test_collection_new_sync.py

@@ -0,0 +1,47 @@
+# ############################################################
+# Importing - Same For All Render Layer Tests
+# ############################################################
+
+import unittest
+import os
+import sys
+
+from view_layer_common import *
+
+
+# ############################################################
+# Testing
+# ############################################################
+
+class UnitTesting(ViewLayerTesting):
+    def test_view_layer_syncing(self):
+        """
+        See if we can copy view layers.
+        """
+        import bpy
+        scene = bpy.context.scene
+        view_layer = scene.view_layers.new("All")
+
+        self.assertEqual(len(view_layer.collections), 1)
+        self.assertEqual(view_layer.collections[0].collection, scene.master_collection)
+
+        self.assertEqual(
+                {collection.name for collection in view_layer.collections[0].collections},
+                {'Collection 1'})
+
+        self.assertEqual(
+                bpy.ops.outliner.collection_new(),
+                {'FINISHED'})
+
+        self.assertEqual(
+                {collection.name for collection in view_layer.collections[0].collections},
+                {'Collection 1', 'Collection 2'})
+
+
+# ############################################################
+# Main - Same For All Render Layer Tests
+# ############################################################
+
+if __name__ == '__main__':
+    UnitTesting._extra_arguments = setup_extra_arguments(__file__)
+    unittest.main()