When the wallet is rescanned at startup in `bitcoind`, there seems to be no way to interrupt that in a clean way (other than forcefully killing the process).
{
    if (IsCoinBase() && GetBlocksToMaturity() > 0 && IsInMainChain())
    {
        if (fUseCache && fImmatureWatchCreditCached)
            return nImmatureWatchCreditCached;
        nImmatureWatchCreditCached = pwallet->GetCredit(*tx, ISMINE_WATCH_ONLY);
        fImmatureWatchCreditCached = true;
        return nImmatureWatchCreditCached;
    }
    return 0;
}
CAmount CWalletTx::GetAvailableWatchOnlyCredit(const bool fUseCache) const