Reverting when cancelling out of edits works for both legacy and new object providers (#3435)

* Update persistence capability to use object api get
* Getting objects using the legacy object service provider will use the defaultSpace if necessary

platform/core/src/capabilities/PersistenceCapability.js

@@ -153,10 +153,11 @@ define(["objectUtils"],
                 return this.$q.when(true);
             }
 
-            return this.persistenceService.readObject(
-                this.getSpace(),
-                this.getKey()
-            ).then(updateModel);
+            return this.openmct.objects.get(domainObject.getId()).then((newStyleObject) => {
+                let oldStyleObject = this.openmct.legacyObject(newStyleObject);
+
+                return updateModel(oldStyleObject.getModel());
+            });
         };
 
         /**