backend: fs implements the Shutdowner interface

Since `tokenRenewer` adds a Shutdown method, we should call it to
clean up resources.

changes backends:
onedrive,box,pcloud,amazonclouddrive,hidrive,jottacloud,sharefile
,premiumizeme

Signed-off-by: rkonfj <rkonfj@gmail.com>

backend/box/box.go

@@ -1207,6 +1207,12 @@ func (f *Fs) CleanUp(ctx context.Context) (err error) {
 	return err
 }
 
+// Shutdown shutdown the fs
+func (f *Fs) Shutdown(ctx context.Context) error {
+	f.tokenRenewer.Shutdown()
+	return nil
+}
+
 // ChangeNotify calls the passed function with a path that has had changes.
 // If the implementation uses polling, it should adhere to the given interval.
 //
@@ -1719,6 +1725,7 @@ var (
 	_ fs.DirCacheFlusher = (*Fs)(nil)
 	_ fs.PublicLinker    = (*Fs)(nil)
 	_ fs.CleanUpper      = (*Fs)(nil)
+	_ fs.Shutdowner      = (*Fs)(nil)
 	_ fs.Object          = (*Object)(nil)
 	_ fs.IDer            = (*Object)(nil)
 )