Merge tag 'ceph-for-7.1-rc5' of https://github.com/ceph/ceph-client

Pull ceph fix from Ilya Dryomov:
 "A fix for an 'rbd unmap' race condition which popped up on a
  production setup where many RBD devices are frequently mapped and
  unmapped, marked for stable"

* tag 'ceph-for-7.1-rc5' of https://github.com/ceph/ceph-client:
  rbd: eliminate a race in lock_dwork draining on unmap