allow service freeze/unfreeze on a setup (#13707)

an active running speedTest will reject all
new S3 requests to the server, until speedTest
is complete.

this is to ensure that speedTest results are
accurate and trusted.

Co-authored-by: Klaus Post <klauspost@gmail.com>

cmd/globals.go

@@ -23,6 +23,7 @@ import (
 	"net/http"
 	"os"
 	"sync"
+	"sync/atomic"
 	"time"
 
 	"github.com/minio/console/restapi"
@@ -325,6 +326,13 @@ var (
 
 	globalConsoleSrv *restapi.Server
 
+	// handles service freeze or un-freeze S3 API calls.
+	globalServiceFreeze atomic.Value
+
+	// Only needed for tracking
+	globalServiceFreezeCnt int32
+	globalServiceFreezeMu  sync.Mutex // Updates.
+
 	// Add new variable global values here.
 )