mount: add retry for all operations with filer

fix https://github.com/chrislusf/seaweedfs/issues/1589

weed/util/retry.go

@@ -0,0 +1,21 @@
+package util
+
+import (
+	"time"
+
+	"github.com/chrislusf/seaweedfs/weed/glog"
+)
+
+func Retry(name string, waitTimeLimit time.Duration, job func() error) (err error) {
+	waitTime := time.Second
+	for waitTime < waitTimeLimit {
+		err = job()
+		if err == nil {
+			break
+		}
+		glog.V(1).Infof("retry %s", name)
+		time.Sleep(waitTime)
+		waitTime += waitTime / 2
+	}
+	return err
+}