ceph: properly put ceph_string reference after async create attempt

stable inclusion
from stable-v5.10.96
commit e7be12ca7d3947765b0d7c1c7e0537e748da993a
bugzilla: https://gitee.com/openeuler/kernel/issues/I55NWB

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=e7be12ca7d3947765b0d7c1c7e0537e748da993a



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commit 932a9b58 upstream.

The reference acquired by try_prep_async_create is currently leaked.
Ensure we put it.

Cc: stable@vger.kernel.org
Fixes: 9a8d03ca ("ceph: attempt to do async create when possible")
Signed-off-by: Jeff Layton <jlayton@kernel.org>
Reviewed-by: Ilya Dryomov <idryomov@gmail.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Yu Liao <liaoyu15@huawei.com>
Reviewed-by: Wei Li <liwei391@huawei.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>