pkg/kubectl: preallocate slice

To avoid slice growth with append operations.

pkg/kubectl/kubectl.go

@@ -43,7 +43,7 @@ type NamespaceInfo struct {
 }
 
 func listOfImages(spec *api.PodSpec) []string {
-	var images []string
+	images := make([]string, 0, len(spec.Containers))
 	for _, container := range spec.Containers {
 		images = append(images, container.Image)
 	}
@@ -64,7 +64,7 @@ func NewThirdPartyResourceMapper(gvs []unversioned.GroupVersion, gvks []unversio
 				}, nil
 			}
 		}
-		groupVersions := []string{}
+		groupVersions := make([]string, 0, len(gvs))
 		for ix := range gvs {
 			groupVersions = append(groupVersions, gvs[ix].String())
 		}