Opening two of the same wallet (tested in v0.18.0 of bitcoin-qt 64 bit) will cause a database collision, and will crash the program.

`[marshall@likon] {21:21} [~] $ bitcoin-0.18.0/bin/bitcoin-qt `
`terminate called after throwing an instance of 'std::runtime_error'  what():  BerkeleyBatch: Can't open database 8204388-wallet.dat (duplicates fileid 8b1c090000000800e25686350000000000000000 from 1352491-wallet.dat)`
`Aborted (core dumped)`

I have been able to reproduce the issue by importing two of the same wallet (with different filenames).
{
    DBErrors nZapWalletTxRet = WalletBatch(*database,"cr+").ZapWalletTx(vWtx);
    if (nZapWalletTxRet == DBErrors::NEED_REWRITE)
    {
        if (database->Rewrite("\x04pool"))
        {
            for (const auto& spk_man_pair : m_spk_managers) {
                spk_man_pair.second->RewriteDB();
            }
        }
    }
    if (nZapWalletTxRet != DBErrors::LOAD_OK)
        return nZapWalletTxRet;
    return DBErrors::LOAD_OK;
}
bool CWallet::SetAddressBookWithDB(WalletBatch& batch, const CTxDestination& address, const std::string& strName, const std::string& strPurpose)