Remove container.When method

Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@crosbymichael.com> (github: crosbymichael)

runtime/container.go

@@ -112,10 +112,6 @@ func (container *Container) Inject(file io.Reader, pth string) error {
 	return nil
 }
 
-func (container *Container) When() time.Time {
-	return container.Created
-}
-
 func (container *Container) FromDisk() error {
 	data, err := ioutil.ReadFile(container.jsonPath())
 	if err != nil {

runtime/history.go

@@ -14,7 +14,7 @@ func (history *History) Len() int {
 
 func (history *History) Less(i, j int) bool {
 	containers := *history
-	return containers[j].When().Before(containers[i].When())
+	return containers[j].Created.Before(containers[i].Created)
 }
 
 func (history *History) Swap(i, j int) {