Lock container when deleting its root directory

Attempting to delete the directory while another goroutine is
concurrently executing a CheckpointTo() can fail on Windows due to file
locking. As all callers of CheckpointTo() are required to hold the
container lock, holding the lock while deleting the directory ensures
that there will be no interference.

Signed-off-by: Cory Snider <csnider@mirantis.com>

daemon/delete.go

@@ -138,7 +138,14 @@ func (daemon *Daemon) cleanupContainer(container *container.Container, config ty
 		container.RWLayer = nil
 	}
 
-	if err := containerfs.EnsureRemoveAll(container.Root); err != nil {
+	// Hold the container lock while deleting the container root directory
+	// so that other goroutines don't attempt to concurrently open files
+	// within it. Having any file open on Windows (without the
+	// FILE_SHARE_DELETE flag) will block it from being deleted.
+	container.Lock()
+	err := containerfs.EnsureRemoveAll(container.Root)
+	container.Unlock()
+	if err != nil {
 		err = errors.Wrapf(err, "unable to remove filesystem for %s", container.ID)
 		container.SetRemovalError(err)
 		return err