stake-pool: Refresh blockhash earlier (solana-labs#3988)

Author: joncinque

stake-pool/program/tests/withdraw.rs

@@ -632,22 +632,22 @@ async fn fail_with_not_enough_tokens() {
         tokens_to_burn,
     ) = setup_for_withdraw(spl_token::id()).await;
 
+    let last_blockhash = context
+        .banks_client
+        .get_new_latest_blockhash(&context.last_blockhash)
+        .await
+        .unwrap();
+
     // Empty validator stake account
     let empty_stake_account = simple_add_validator_to_pool(
         &mut context.banks_client,
         &context.payer,
-        &context.last_blockhash,
+        &last_blockhash,
         &stake_pool_accounts,
         None,
     )
     .await;
 
-    let last_blockhash = context
-        .banks_client
-        .get_new_latest_blockhash(&context.last_blockhash)
-        .await
-        .unwrap();
-
     let new_authority = Pubkey::new_unique();
     let error = stake_pool_accounts
         .withdraw_stake(