Merge pull request #12041 from yangdongsheng/rbd_mirror_clone

librbd: asynchronous clone state machine

Reviewed-by: Jason Dillaman <dillaman@redhat.com>

diff --cc src/librbd/internal.cc
Simple merge

diff --cc src/librbd/internal.h
Simple merge

diff --cc src/librbd/librbd.cc
Simple merge

diff --cc src/test/rbd_mirror/image_replayer/test_mock_CreateImageRequest.cc
Simple merge

diff --cc src/tools/rbd_mirror/image_replayer/CreateImageRequest.cc
Simple merge