ceph: update dentry lease for async create

Otherwise ceph_d_delete() may return 1 for the dentry, which makes
dput() prune the dentry and clear parent dir's complete flag.

Signed-off-by: "Yan, Zheng" <zyan@redhat.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>