Merge pull request #7649 from yuyuyu101/wip-async-watch

librados: implement async watch/unwatch

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

diff --cc src/include/rados/librados.h
Simple merge

diff --cc src/include/rados/librados.hpp
Simple merge

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

diff --cc src/osdc/Objecter.cc
Simple merge

diff --cc src/osdc/Objecter.h
Simple merge