osd/ReplicatedPG: strengthen agent_work assertions

Signed-off-by: Sage Weil <sage@inktank.com>
osd/ReplicatedPG: load older HitSets into memory

If our evict_mode is non-idle, load older HitSets into memory in the agent
work thread.

Signed-off-by: Sage Weil <sage@inktank.com>
osd/ReplicatedPG: EOPNOTSUPP on hit_set_get on non-replicated pools

We need to use the async read stuff for this to work.

Signed-off-by: Sage Weil <sage@inktank.com>
Merge pull request #1257 from ceph/wip-agent

osd: a few agent fixes

Reviewed-by: Samuel Just <sam.just@inktank.com>