fixup! Handling Pausing from freezer state

Avoid a racy Stat call (the filesystem could be removed after the Stat
but before the ReadFile).

Signed-off-by: W. Trevor King <wking@tremily.us>

Author: wking

libcontainer/container_linux.go

@@ -769,13 +769,11 @@ func (c *linuxContainer) updateState(process parentProcess) error {
 
 func (c *linuxContainer) checkFreezer() (Status, error) {
 	path := c.cgroupManager.GetPaths()["freezer"]
-	if _, err := os.Stat(path); err != nil {
+	contents, err := ioutil.ReadFile(filepath.Join(path, "freezer.state"))
+	if err != nil {
 		if os.IsNotExist(err) {
 			return Running, nil
 		}
-	}
-	contents, err := ioutil.ReadFile(filepath.Join(path, "freezer.state"))
-	if err != nil {
 		return 0, newSystemError(err)
 	}
 	freezerstate := string(contents)