Bump default idleConnsPerHost to control conns in time_wait (#10653)

This PR fixes a hang which occurs quite commonly at higher concurrency
by allowing following changes

- allowing lower connections in time_wait allows faster socket open's
- lower idle connection timeout to ensure that we let kernel
  reclaim the time_wait connections quickly
- increase somaxconn to 4096 instead of 2048 to allow larger tcp
  syn backlogs.

fixes #10413

cmd/iam.go

@@ -408,13 +408,6 @@ func (sys *IAMSys) doIAMConfigMigration(ctx context.Context) error {
 	return sys.store.migrateBackendFormat(ctx)
 }
 
-// Loads IAM users and policies in background, any un-handled
-// error means this code can potentially crash the server
-// in such a situation manual intervention is necessary.
-func startBackgroundIAMLoad(ctx context.Context, objAPI ObjectLayer) {
-	go globalIAMSys.Init(ctx, objAPI)
-}
-
 // Init - initializes config system by reading entries from config/iam
 func (sys *IAMSys) Init(ctx context.Context, objAPI ObjectLayer) {
 	if objAPI == nil {