Unable to unlock every UTXO using lockunspent

[chris-belcher]

The call lockunspent allows unlocking every UTXO, but I think this cant be done with rust-bitcoincore-rpc.

The way to unlock everything is to just pass true, but the way the call is currently implemented always passes another list (e.g. true []). Even if that list is empty Core will not unlock everything.

Examples:

let rpc: Client;
rpc.unlock_unspent(&[]); //does not unlock every UTXO
rpc.call("lockunspent", &[Value::Bool(true)]); //does unlock every UTXO