Merge pull request #26519 from idryomov/wip-cmpext-bl

librbd: ensure compare-and-write doesn't skip compare after copyup

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

diff --cc src/test/librados_test_stub/LibradosTestStub.cc
Simple merge

diff --cc src/test/librados_test_stub/TestMemIoCtxImpl.cc
Simple merge

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