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).
{
    CCrypter crypter;
    CKeyingMaterial _vMasterKey;
    {
        LOCK(cs_wallet);
        for (const MasterKeyMap::value_type& pMasterKey : mapMasterKeys)
        {
            if(!crypter.SetKeyFromPassphrase(strWalletPassphrase, pMasterKey.second.vchSalt, pMasterKey.second.nDeriveIterations, pMasterKey.second.nDerivationMethod))
                return false;
            if (!crypter.Decrypt(pMasterKey.second.vchCryptedKey, _vMasterKey))
                continue; 
            if (Unlock(_vMasterKey, accept_no_keys)) {
                
                UpgradeKeyMetadata();
                return true;
            }
        }
    }
    return false;
}
bool CWallet::ChangeWalletPassphrase(const SecureString& strOldWalletPassphrase, const SecureString& strNewWalletPassphrase)
{
    bool fWasLocked = IsLocked();
    {
        LOCK(cs_wallet);
        Lock();
        CCrypter crypter;
        CKeyingMaterial _vMasterKey;
        for (MasterKeyMap::value_type& pMasterKey : mapMasterKeys)