client: fix directory inode can not call release callback

client: fix directory inode can not call release callback

When use client like nfs-ganesha hold ref of dir inode,
the dentry of the inode does not expirable because its
state is always lru_pinned.

The current code location does not tell nfs-ganesha to
release dir inodes, so we should call release_callback
to tell nfs-ganesha release first, and then trim dentry
when its state becomes unpin.

Fixes: https://tracker.ceph.com/issues/46355
Signed-off-by: sepia-liu <liuwei_coder@163.com>