clear cache directory when mount exits (#6605)

Signed-off-by: lizhengui <lizhengui@virtaitech.com>
Co-authored-by: lizhengui <lizhengui@virtaitech.com>

weed/command/mount_std.go

@@ -284,5 +284,7 @@ func RunMount(option *MountOptions, umask os.FileMode) bool {
 
 	server.Serve()
 
+	seaweedFileSystem.ClearCacheDir()
+
 	return true
 }

weed/mount/weedfs.go

@@ -224,6 +224,12 @@ func (wfs *WFS) getCurrentFiler() pb.ServerAddress {
 	return wfs.option.FilerAddresses[i]
 }
 
+func (wfs *WFS) ClearCacheDir() {
+	wfs.metaCache.Shutdown()
+	os.RemoveAll(wfs.option.getUniqueCacheDirForWrite())
+	os.RemoveAll(wfs.option.getUniqueCacheDirForRead())
+}
+
 func (option *Option) setupUniqueCacheDirectory() {
 	cacheUniqueId := util.Md5String([]byte(option.MountDirectory + string(option.FilerAddresses[0]) + option.FilerMountRootPath + util.Version()))[0:8]
 	option.uniqueCacheDirForRead = path.Join(option.CacheDirForRead, cacheUniqueId)