fix: heal bucket metadata right before healing bucket (#11097)

optimization mainly to avoid listing the entire
`.minio.sys/buckets/.minio.sys` directory, this
can get really huge and comes in the way of startup
routines, contents inside `.minio.sys/buckets/.minio.sys`
are rather transient and not necessary to be healed.

cmd/service.go

@@ -45,11 +45,6 @@ var GlobalContext context.Context
 // cancelGlobalContext can be used to indicate server shutdown.
 var cancelGlobalContext context.CancelFunc
 
-// Initialize service mutex once.
-func init() {
-	initGlobalContext()
-}
-
 func initGlobalContext() {
 	GlobalContext, cancelGlobalContext = context.WithCancel(context.Background())
 	GlobalServiceDoneCh = GlobalContext.Done()