Fix feerate coin control

Summary:
Fixes failing rpc_fundrawtransaction test on master due to botched backport D2673
Initially, it was thought that the entirety of the CoinControl block in GetMinimumFee was not needed since we're
not backporting the RBF and other fee-rated controls. However, this missed the case where this block was removed
from wallet.cpp and did not have a replacement:

if (coinControl && coinControl->fOverrideFeeRate) {
    nFeeNeeded = coinControl->nFeeRate.GetFeeCeiling(nBytes);
}

Test Plan:
make check
test_runner.py --extended

Reviewers: deadalnix, Fabien, #bitcoin_abc

Reviewed By: Fabien, #bitcoin_abc

Subscribers: teamcity, schancel

Differential Revision: https://reviews.bitcoinabc.org/D2683