net: use Sock::SetSockOpt() instead of standalone SetSocketNoDelay()

Since the former is mockable, this makes it easier to test higher level
code that sets the TCP_NODELAY flag.

src/net.cpp

@@ -1190,7 +1190,11 @@ void CConnman::CreateNodeFromAcceptedSocket(std::unique_ptr<Sock>&& sock,
 
     // According to the internet TCP_NODELAY is not carried into accepted sockets
     // on all platforms.  Set it again here just to be sure.
-    SetSocketNoDelay(sock->Get());
+    const int on{1};
+    if (sock->SetSockOpt(IPPROTO_TCP, TCP_NODELAY, &on, sizeof(on)) == SOCKET_ERROR) {
+        LogPrint(BCLog::NET, "connection from %s: unable to set TCP_NODELAY, continuing anyway\n",
+                 addr.ToString());
+    }
 
     // Don't accept connections from banned peers.
     bool banned = m_banman && m_banman->IsBanned(addr);