Update variables as returned by useRequest

Update variables to be consistent with variables returned by useRequest.

awx/ui_next/src/components/Schedule/shared/ScheduleForm.jsx

@@ -223,7 +223,7 @@ function ScheduleForm({
   const {
     request: loadScheduleData,
     error: contentError,
-    contentLoading,
+    isLoading: contentLoading,
     result: { zoneOptions, credentials },
   } = useRequest(
     useCallback(async () => {

awx/ui_next/src/components/Schedule/shared/ScheduleForm.test.jsx

@@ -447,6 +447,7 @@ describe('<ScheduleForm />', () => {
           />
         );
       });
+      await waitForElement(wrapper, 'ContentLoading', el => el.length === 0);
     });
     afterAll(() => {
       wrapper.unmount();