message: snapshotter: add DisableIndexedMap blobcache config in daemonconfig
  So we could control it via snapshotter.
diff: @@ -83,6 +83,7 @@ type DeviceConfig struct {
  Compressed bool `json:"compressed,omitempty"`
  Config struct {
  WorkDir string `json:"work_dir"`
  + DisableIndexedMap bool `json:"disable_indexed_map"`
  } `json:"config"`
  } `json:"cache"`
  }
  