ui: Ensure datacenter is sent to the API when loading in a policy panel (#7910)

* ui: Policies don't have datacenter properties, use the URL dc instead.

* ui: Ensure policy saving proxy object is destroyed

ui-v2/app/components/child-selector/index.js

@@ -76,9 +76,13 @@ export default Component.extend(SlotsMixin, WithListeners, {
             items,
             e.data,
           ]);
+          item.willDestroy();
           success();
         },
-        error: e => this.error(e),
+        error: e => {
+          item.willDestroy();
+          this.error(e);
+        },
       });
     },
     remove: function(item, items) {

ui-v2/app/components/policy-selector/index.hbs

@@ -59,7 +59,7 @@
       <BlockSlot @name="details">
           {{#if (eq item.template '')}}
             <DataSource
-              @src={{concat '/' item.Namespace '/' item.Datacenter '/policy/' item.ID}}
+              @src={{concat '/' item.Namespace '/' dc '/policy/' item.ID}}
               @onchange={{action (mut loadedItem) value="data"}}
               @loading="lazy"
             />