MDL-40389 Test "parent" course/category generators

Verify that the category->parent switchers for
course & category behat generators are happening
as expected. Use the manage courses page for that.

admin/tool/behat/tests/behat/data_generators.feature

@@ -30,6 +30,17 @@ Feature: Set up contextual data for tests
     Then I should see "Course 1"
     And I should see "Course 2"
     And I should see "Course 3"
+    When I go to the courses management page
+    And I follow "Cat 1"
+    Then I should see "Cat 2"
+    And I should see "Cat 3"
+    When I follow "Cat 3"
+    Then I should see "Course 1"
+    And I should see "Course 2"
+    When I select "Cat 2" from "Course categories:"
+    Then I should see "No courses in this category"
+    When I select "Miscellaneous" from "Course categories:"
+    Then I should see "Course 3"
 
   @javascript
   Scenario: Add a bunch of groups and groupings