Objecter: add "honor_cache_redirects" flag covering cache settings

When set to false, we do not redirect based on the cache_pool data
in the OSDMap. We'll use this so the OSDs can actually fetch data
into the cache pools on promotion!
Signed-off-by: Greg Farnum <greg@inktank.com>
OSD: unset_honor_cache_redirects() on Objecter

Signed-off-by: Greg Farnum <greg@inktank.com>
Merge pull request #659 from ceph/wip-objecter-notier

Wip objecter notier

Reviewed-by: Sage Weil <sage@inktank.com>