Fix staking amount

[Thoralf-M]

Description of change

Fix staking amount when start staking and also don't set the account output amount to min amount when extending staking

Links to any relevant issues

Fixes #2236

Type of change

• Bug fix (a non-breaking change which fixes an issue)

How the change has been tested

Staked the full amount with the cli

Balance {
    base_coin: BaseCoinBalance {
        total: 2000000000,
...
Wallet "wallet": begin-staking 0xac7470df11783cdc153689da2a0bd138c99dc351f530099538afadb4b5a89b14 2000000000 2
Stronghold password: [hidden]
Begin staking for 0xac7470df11783cdc153689da2a0bd138c99dc351f530099538afadb4b5a89b14.
Begin staking transaction sent:
TransactionId { id: "0xb4c36cb18b6085e8c21dc494a05273f62fe1489ba764a8d6892538c8d02d00f4c9270100", slot_index: SlotIndex(75721) }
Some(BlockId { id: "0xf9ed06be0122e4328c19207d987a15e8ac663e40c1aebac2692c0d891f0bd058c9270100", slot_index: SlotIndex(75721) })