delayed locks until we have started reading the body (#10474)

This is to ensure that Go contexts work properly, after some
interesting experiments I found that Go net/http doesn't
cancel the context when Body is non-zero and hasn't been
read till EOF.

The following gist explains this, this can lead to pile up
of go-routines on the server which will never be canceled
and will die at a really later point in time, which can
simply overwhelm the server.

https://gist.github.com/harshavardhana/c51dcfd055780eaeb71db54f9c589150

To avoid this refactor the locking such that we take locks after we
have started reading from the body and only take locks when needed.

Also, remove contextReader as it's not useful, doesn't work as expected
context is not canceled until the body reaches EOF so there is no point
in wrapping it with context and putting a `select {` on it which
can unnecessarily increase the CPU overhead.

We will still use the context to cancel the lockers etc.
Additional simplification in the locker code to avoid timers
as re-using them is a complicated ordeal avoid them in
the hot path, since locking is very common this may avoid
lots of allocations.

cmd/server-main.go

@@ -17,12 +17,9 @@
 package cmd
 
 import (
-	"bufio"
 	"context"
 	"errors"
 	"fmt"
-	"io"
-	"log"
 	"net"
 	"os"
 	"os/signal"
@@ -247,7 +244,7 @@ func initSafeMode(ctx context.Context, newObject ObjectLayer) (err error) {
 	//    version is needed, migration is needed etc.
 	rquorum := InsufficientReadQuorum{}
 	wquorum := InsufficientWriteQuorum{}
-	for range retry.NewTimer(retryCtx) {
+	for range retry.NewTimerWithJitter(retryCtx, 250*time.Millisecond, 500*time.Millisecond, retry.MaxJitter) {
 		// let one of the server acquire the lock, if not let them timeout.
 		// which shall be retried again by this loop.
 		if err = txnLk.GetLock(configLockTimeout); err != nil {
@@ -462,27 +459,7 @@ func serverMain(ctx *cli.Context) {
 		getCert = globalTLSCerts.GetCertificate
 	}
 
-	// Annonying hack to ensure that Go doesn't write its own logging,
-	// interleaved with our formatted logging, this allows us to
-	// honor --json and --quiet flag properly.
-	//
-	// Unfortunately we have to resort to this sort of hacky approach
-	// because, Go automatically initializes ErrorLog on its own
-	// and can log without application control.
-	//
-	// This is an implementation issue in Go and should be fixed, but
-	// until then this hack is okay and works for our needs.
-	pr, pw := io.Pipe()
-	go func() {
-		defer pr.Close()
-		scanner := bufio.NewScanner(&contextReader{pr, GlobalContext})
-		for scanner.Scan() {
-			logger.LogIf(GlobalContext, errors.New(scanner.Text()))
-		}
-	}()
-
 	httpServer := xhttp.NewServer([]string{globalMinioAddr}, criticalErrorHandler{corsHandler(handler)}, getCert)
-	httpServer.ErrorLog = log.New(pw, "", 0)
 	httpServer.BaseContext = func(listener net.Listener) context.Context {
 		return GlobalContext
 	}