net/ceph: unbreak with boost 1.67

src/rbd_replay/Replayer.cc:353:65: error: no matching conversion for functional-style cast from 'float' to 'boost::posix_time::microseconds' (aka 'subsecond_duration<boost::posix_time::time_duration, 1000000>')

boost::system_time sub_release_time(action_completed_time + boost::posix_time::microseconds(dep.time_delta * m_latency_multiplier / 1000));
                                                            ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

PR: 227427
Reported by: antoine (via exp-run)