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);

src/netbase.cpp

@@ -519,7 +519,10 @@ std::unique_ptr<Sock> CreateSockTCP(const CService& address_family)
 #endif
 
     // Set the no-delay option (disable Nagle's algorithm) on the TCP socket.
-    SetSocketNoDelay(sock->Get());
+    const int on{1};
+    if (sock->SetSockOpt(IPPROTO_TCP, TCP_NODELAY, &on, sizeof(on)) == SOCKET_ERROR) {
+        LogPrint(BCLog::NET, "Unable to set TCP_NODELAY on a newly created socket, continuing anyway\n");
+    }
 
     // Set the non-blocking option on the socket.
     if (!SetSocketNonBlocking(sock->Get())) {
@@ -729,13 +732,6 @@ bool SetSocketNonBlocking(const SOCKET& hSocket)
     return true;
 }
 
-bool SetSocketNoDelay(const SOCKET& hSocket)
-{
-    int set = 1;
-    int rc = setsockopt(hSocket, IPPROTO_TCP, TCP_NODELAY, (const char*)&set, sizeof(int));
-    return rc == 0;
-}
-
 void InterruptSocks5(bool interrupt)
 {
     interruptSocks5Recv = interrupt;

src/netbase.h

@@ -223,8 +223,6 @@ bool ConnectThroughProxy(const Proxy& proxy, const std::string& strDest, uint16_
 
 /** Enable non-blocking mode for a socket */
 bool SetSocketNonBlocking(const SOCKET& hSocket);
-/** Set the TCP_NODELAY flag on a socket */
-bool SetSocketNoDelay(const SOCKET& hSocket);
 void InterruptSocks5(bool interrupt);
 
 /**