rpc: Make unloadwallet wait for complete wallet unload

src/wallet/rpcwallet.cpp

@@ -2625,16 +2625,8 @@ static UniValue unloadwallet(const JSONRPCRequest& request)
     if (!RemoveWallet(wallet)) {
         throw JSONRPCError(RPC_MISC_ERROR, "Requested wallet already unloaded");
     }
-    UnregisterValidationInterface(wallet.get());
 
-    // The wallet can be in use so it's not possible to explicitly unload here.
-    // Just notify the unload intent so that all shared pointers are released.
-    // The wallet will be destroyed once the last shared pointer is released.
-    wallet->NotifyUnload();
-
-    // There's no point in waiting for the wallet to unload.
-    // At this point this method should never fail. The unloading could only
-    // fail due to an unexpected error which would cause a process termination.
+    UnloadWallet(std::move(wallet));
 
     return NullUniValue;
 }