Use PohRecorder to synchronize instead of rotate. (#3080)

tests/rpc.rs

@@ -17,7 +17,6 @@ fn test_rpc_send_tx() {
     solana_logger::setup();
 
     let (server, leader_data, alice, ledger_path) = new_fullnode();
-    let server_exit = server.run(None);
     let bob_pubkey = Keypair::new().pubkey();
 
     let client = reqwest::Client::new();
@@ -93,6 +92,6 @@ fn test_rpc_send_tx() {
 
     assert_eq!(confirmed_tx, true);
 
-    server_exit();
+    server.close().unwrap();
     remove_dir_all(ledger_path).unwrap();
 }