Revert "mount: remove mount directory from generating cache directory id"

This reverts commit 109dc7fdf6.

weed/mount/weedfs.go

@@ -190,7 +190,7 @@ func (wfs *WFS) getCurrentFiler() pb.ServerAddress {
 }
 
 func (option *Option) setupUniqueCacheDirectory() {
-	cacheUniqueId := util.Md5String([]byte(string(option.FilerAddresses[0]) + option.FilerMountRootPath + util.Version()))[0:8]
+	cacheUniqueId := util.Md5String([]byte(option.MountDirectory + string(option.FilerAddresses[0]) + option.FilerMountRootPath + util.Version()))[0:8]
 	option.uniqueCacheDir = path.Join(option.CacheDir, cacheUniqueId)
 	option.uniqueCacheTempPageDir = filepath.Join(option.uniqueCacheDir, "swap")
 	os.MkdirAll(option.uniqueCacheTempPageDir, os.FileMode(0777)&^option.Umask)