add '.healing.bin' for tracking currently healing disk (#10573)

add a hint on the disk to allow for tracking fresh disk
being healed, to allow for restartable heals, and also
use this as a way to track and remove disks.

There are more pending changes where we should move
all the disk formatting logic to backend drives, this
PR doesn't deal with this refactor instead makes it
easier to track healing in the future.

cmd/http/server.go

@@ -130,6 +130,9 @@ func (srv *Server) Shutdown() error {
 	srv.listenerMutex.Lock()
 	err := srv.listener.Close()
 	srv.listenerMutex.Unlock()
+	if err != nil {
+		return err
+	}
 
 	// Wait for opened connection to be closed up to Shutdown timeout.
 	shutdownTimeout := srv.ShutdownTimeout
@@ -144,12 +147,12 @@ func (srv *Server) Shutdown() error {
 			if err == nil {
 				_ = pprof.Lookup("goroutine").WriteTo(tmp, 1)
 				tmp.Close()
-				return errors.New("timed out. some connections are still active. doing abnormal shutdown. goroutines written to " + tmp.Name())
+				return errors.New("timed out. some connections are still active. goroutines written to " + tmp.Name())
 			}
-			return errors.New("timed out. some connections are still active. doing abnormal shutdown")
+			return errors.New("timed out. some connections are still active")
 		case <-ticker.C:
 			if atomic.LoadInt32(&srv.requestCount) <= 0 {
-				return err
+				return nil
 			}
 		}
 	}