message: Fix hackatom integration tests with configurable storage
diff: #![cfg(feature = "integration")]
  use cosmwasm::serde::{from_slice, to_vec};
  +use cosmwasm::mock::MockStorage;
  use cosmwasm::storage::Storage;
  use cosmwasm::types::{coin, mock_params, CosmosMsg};
  use cosmwasm_vm::{call_handle, call_init, instantiate, with_storage};
  @@ -22,7 +23,8 @@ static WASM: &[u8] = include_bytes!("../target/wasm32-unknown-unknown/release/ha
  #[test]
  fn successful_init_and_handle() {
  assert!(WASM.len() > 100000);
  - let mut instance = instantiate(&WASM);
  + let storage = MockStorage::new();
  + let mut instance = instantiate(&WASM, storage);
  // prepare arguments
  let params = mock_params("creator", &coin("1000", "earth"), &[]);
  @@ -61,7 +63,7 @@ fn successful_init_and_handle() {
  }
  // we can check the storage as well
  - with_storage(&instance, |store| {
  + with_storage(&instance, |store: &mut MockStorage| {
  let foo = store.get(b"foo");
  assert!(foo.is_none());
  let data = store.get(CONFIG_KEY).expect("no data stored");
  @@ -72,7 +74,8 @@ fn successful_init_and_handle() {
  #[test]
  fn failed_handle() {
  - let mut instance = instantiate(&WASM);
  + let storage = MockStorage::new();
  + let mut instance = instantiate(&WASM, storage);
  // initialize the store
  let init_msg = to_vec(&InitMsg {
  @@ -91,7 +94,7 @@ fn failed_handle() {
  assert!(handle_res.is_err());
  // state should be saved
  - with_storage(&instance, |store| {
  + with_storage(&instance, |store: &mut MockStorage| {
  let data = store.get(CONFIG_KEY).expect("no data stored");
  let state: State = from_slice(&data).unwrap();
  assert_eq!(state.verifier, String::from("verifies"));
  