osd/osd_types: add num_bytes_hit_set_archive to stats

The tiering agent's life is easier/better if it knows how many bytes these
objects consume (instead of making a conservative guess).

Signed-off-by: Sage Weil <sage@redhat.com>
osd/ReplicatedPG: account for hit_set_archive bytes

Signed-off-by: Sage Weil <sage@redhat.com>
osd/ReplicatedPG: scrub and repair hit_set_archive bytes

Signed-off-by: Sage Weil <sage@redhat.com>
osd/ReplicatedPG: calculate num_user_bytes

This is the bytes stored by the user, excluding hit_sets.

Signed-off-by: Sage Weil <sage@redhat.com>
osd/ReplicatedPG: adjust avg_size calculation in agent_choose_mode

Signed-off-by: Zhiqiang Wang <wonzhq@hotmail.com>