message: [Types] Fix warning
  ```
  Compiling types v0.1.0 (/Users/wqfish/github/libra/types)
  warning: unused import: `crypto::HashValue`
  --> types/src/account_config.rs:19:5
  |
  19 | use crypto::HashValue;
  |     ^^^^^^^^^^^^^^^^^
  |
  = note: #[warn(unused_imports)] on by default
  ```
diff: @@ -16,6 +16,7 @@ use canonical_serialization::{
  CanonicalDeserialize, CanonicalDeserializer, CanonicalSerialize, CanonicalSerializer,
  SimpleDeserializer,
  };
  +#[cfg(any(test, feature = "testing"))]
  use crypto::HashValue;
  use failure::prelude::*;
  #[cfg(any(test, feature = "testing"))]
  