message: test: Rename wallet.dat to wallet_test.dat
  Indicate that the file name is not hardcoded, and a little bit of safety
  so that it never nukes the main wallet.
  Suggestion by Marco Falke.
diff: @@ -10,7 +10,7 @@ WalletTestingSetup::WalletTestingSetup(const std::string& chainName):
  bitdb.MakeMock();
  bool fFirstRun;
  - pwalletMain = new CWallet("wallet.dat");
  + pwalletMain = new CWallet("wallet_test.dat");
  pwalletMain->LoadWallet(fFirstRun);
  RegisterValidationInterface(pwalletMain);
  