Allow for filtering/sorting by reserved fields

Certain fields like "type" in an object are reserved by
rancher/apiserver and so are transmuted to an underscore-prefixed
version of the field name, e.g. "_type", which is what appears in the
HTTP response output. Objects like Secrets, which have a built-in Type
field, are subject to this.

Without this patch, filtering and sorting are done on the object prior
to the field renaming, so filtering by "_type" would result in no
filtering happening even though the output returned to the user does
contain "_type". This change ensures that the field name changes happen
before filtering and sorting is started.

pkg/stores/partition/listprocessor/processor.go

@@ -260,17 +260,15 @@ func getLimit(apiOp *types.APIRequest) int {
 
 // FilterList accepts a channel of unstructured objects and a slice of filters and returns the filtered list.
 // Filters are ANDed together.
-func FilterList(list <-chan []unstructured.Unstructured, filters []OrFilter) []unstructured.Unstructured {
+func FilterList(list []unstructured.Unstructured, filters []OrFilter) []unstructured.Unstructured {
 	result := []unstructured.Unstructured{}
-	for items := range list {
-		for _, item := range items {
-			if len(filters) == 0 {
-				result = append(result, item)
-				continue
-			}
-			if matchesAll(item.Object, filters) {
-				result = append(result, item)
-			}
+	for _, item := range list {
+		if len(filters) == 0 {
+			result = append(result, item)
+			continue
+		}
+		if matchesAll(item.Object, filters) {
+			result = append(result, item)
 		}
 	}
 	return result