[build] remove #ifdef ENABLE_WALLET from interfaces/node

Removes the final #ifdef ENABLE_WALLET from libbitcoin_server by calling
g_wallet_init_interface.HasWalletSupport(), and redifining GetWallets()
and MakeWallet() in dummywallet.cpp.

src/dummywallet.cpp

@@ -6,6 +6,8 @@
 #include <util.h>
 #include <walletinitinterface.h>
 
+class CWallet;
+
 class DummyWalletInit : public WalletInitInterface {
 public:
 
@@ -31,3 +33,19 @@ void DummyWalletInit::AddWalletOptions() const
 }
 
 const WalletInitInterface& g_wallet_init_interface = DummyWalletInit();
+
+std::vector<std::shared_ptr<CWallet>> GetWallets()
+{
+    throw std::logic_error("Wallet function called in non-wallet build.");
+}
+
+namespace interfaces {
+
+class Wallet;
+
+std::unique_ptr<Wallet> MakeWallet(const std::shared_ptr<CWallet>& wallet)
+{
+    throw std::logic_error("Wallet function called in non-wallet build.");
+}
+
+} // namespace interfaces