osd/ReplicatedPG: do not update current_last_update on activate

Don't update this when we apply the log to our in-memory hitset!  We should
only update this when we persist something to disk.

Signed-off-by: Sage Weil <sage@inktank.com>
osd/ReplicatedPG: debug: improve hit_set func banners

Signed-off-by: Sage Weil <sage@inktank.com>