message: [secure-storage] make vault internal logic only visible to local crate
  per title
  Closes:
  Approved by: mimoo
diff: @@ -14,7 +14,7 @@ use libra_vault_client::{self as vault, Client};
  /// calls pointers to data keys, Vault has actually a secret that contains multiple key value
  /// pairs.
  pub struct VaultStorage {
  - pub client: Client,
  + pub(crate) client: Client,
  }
  impl VaultStorage {
  