[RPC] Fee reported by gettransaction is incorrect

## Describe the issue

Since updating to the latest version of bitcoin abc the gettransaction RPC endpoint returns absurdly high values for fees.

### Can you reliably reproduce the issue?
#### If so, please list the steps to reproduce below:
1. Import address
2. Wait for resync to finish
3. Retrieve one transaction

bitcoin-cli importaddress qryz5e9nxtexve3z3ah94mlj30z4fctp5y8kaahzuw "" true
bitcoin-cli gettransaction f37a8639da8f1f66a634303b132817169a8c29d4fe7256184b9ed5d016bf345f true

```
{
"amount": -24.22919216,
"fee": 20.92919216,
"confirmations": 1670,
"blockhash": "00000000000000000119d866eaa40d1a00c08b6edf364fce61ed2b75a29dcf8d",
"blockindex": 912,
"blocktime": 1567055513,
"txid": "f37a8639da8f1f66a634303b132817169a8c29d4fe7256184b9ed5d016bf345f",
"walletconflicts": [
],
"time": 1568031302,
"timereceived": 1568031505,
[...]
}
```

### Expected behaviour
The fee does not match the actual fee paid in this transaction, which is 0.00015 BCH
https://blockchair.com/bitcoin-cash/transaction/f37a8639da8f1f66a634303b132817169a8c29d4fe7256184b9ed5d016bf345f

### What version of bitcoin-abc are you using?
bitcoin-cli --version
Bitcoin ABC RPC client version v0.19.12.0-29ec9c357