ceph: update the dlease for the hashed dentry when removing

The MDS will always refresh the dentry lease when removing the files
or directories. And if the dentry is still hashed, we can update
the dentry lease and no need to do the lookup from the MDS later.

Signed-off-by: Xiubo Li <xiubli@redhat.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>