Ensure we filter resources by namespace (#842)

This got removed in a recent PR but should not have.

When querying namespaced resources you need the field selector
set. This is not something that can easily be tested in unit tests
since that logic happens on the server side and mocks would not
hit that code.

Fixes #839

Signed-off-by: John Schnake <[email protected]>

pkg/discovery/queries.go

@@ -168,6 +168,10 @@ func QueryResources(
 		}
 	}
 
+	if ns != nil && len(*ns) > 0 {
+		opts.FieldSelector = "metadata.namespace=" + *ns
+	}
+
 	// 3. Execute the query
 	for _, gvr := range resources {
 		lister := func() (*unstructured.UnstructuredList, error) {