Kobe Cranker: Increase success rate (#21)

# Problem

- Noticed [some tx
failures](https://solscan.io/tx/2RXfQQrsexJ5kCsRWg5cyCGoMXzAfqBCtevqufKNdoc8CkmazfSDx8CX7ccYrzXUH9vPUqa985rhEV84Njez7Ava)

# Solution

- Before sending txs, check the flag of
[EpochRewards](https://docs.rs/solana-epoch-rewards/2.2.1/solana_epoch_rewards/struct.EpochRewards.html),
if it's true, sleep 1min, other wise update stake pool

Author: aoikurokawa