refactor: Remove call to ShutdownRequested from HTTPRequest

Pass HTTP server an interrupt object instead of having it depend on shutdown.h
and global shutdown state.

There is no change in behavior in this commit.

src/init.cpp

@@ -690,8 +690,9 @@ static bool AppInitServers(NodeContext& node)
     const ArgsManager& args = *Assert(node.args);
     RPCServer::OnStarted(&OnRPCStarted);
     RPCServer::OnStopped(&OnRPCStopped);
-    if (!InitHTTPServer())
+    if (!InitHTTPServer(*Assert(node.shutdown))) {
         return false;
+    }
     StartRPC();
     node.rpc_interruption_point = RpcInterruptionPoint;
     if (!StartHTTPRPC(&node))