Trigger deep scrubs

Ability to trigger deep scrubs to test the impact of deep scrubbing. In hammer there is supposed to be a ceph.conf tunable that allows specifying a time. If that value can be injected, then we can probably do something along the lines of:

current_time = time
schedule_time = current_time + ramp_time

ceph tell * injectargs --some_scrubbing_schedule_key $schedule_time