message: api: also update fs backends in backends collections
  After remount, the mounted time and backend configurations
  might be changed.
diff: @@ -326,6 +326,9 @@ pub trait NydusDaemon: DaemonStateMachineSubscriber {
  e => DaemonError::Rafs(e),
  })?;
  + // To update mounted time and backend configurations.
  + self.backend_collection().add(&cmd.mountpoint, &cmd)?;
  +
  // Update mounts opaque from UpgradeManager
  if let Some(mut mgr_guard) = self.upgrade_mgr() {
  upgrade::update_mounts_state(&mut mgr_guard, cmd)?;
  