Bump up soMaxConn backlog for listener to 2048 (#6416)

soMaxConn value is 128 on almost all linux systems,
this value is too low for Minio at times when used
against large concurrent workload e.g: spark applications
this causes a sort of SYN flooding observed by the kernel
to allow for large backlog increase this value to 2048.

With this value we do not see anymore SYN flooding
kernel messages.

cmd/http/listen_nix.go

@@ -27,6 +27,9 @@ import (
 var cfg = &tcplisten.Config{
 	DeferAccept: true,
 	FastOpen:    true,
+	// Bump up the soMaxConn value from 128 to 2048 to
+	// handle large incoming concurrent requests.
+	Backlog: 2048,
 }
 
 // Unix listener with special TCP options.