message: [Fix] default public key for mnb
diff: @@ -160,7 +160,7 @@ public:
  uint256 GetSignatureHash() const override;
  std::string GetStrMessage() const override;
  const CTxIn GetVin() const override { return vin; };
  - const CPubKey GetPublicKey(std::string& strErrorRet) const override { return pubKeyMasternode; }
  + const CPubKey GetPublicKey(std::string& strErrorRet) const override { return pubKeyCollateralAddress; }
  void swap(CMasternode& first, CMasternode& second) // nothrow
  {
  