message: [Wallet] Fix GetImmatureZerocoinBalance
  need to use `GetUnconfirmedZerocoinBalance()` instead of
  `GetUnconfirmedBalance()` here.
diff: @@ -1601,7 +1601,7 @@ CAmount CWallet::GetZerocoinBalance(bool fMatureOnly) const
  CAmount CWallet::GetImmatureZerocoinBalance() const
  {
  - return GetZerocoinBalance(false) - GetZerocoinBalance(true) - GetUnconfirmedBalance();
  + return GetZerocoinBalance(false) - GetZerocoinBalance(true) - GetUnconfirmedZerocoinBalance();
  }
  CAmount CWallet::GetUnconfirmedZerocoinBalance() const
  