osd: recency should look at newest (not oldest) hitsets

Reported-by: xinxin shu <xinxin.shu@intel.com>
Signed-off-by: Sage Weil <sage@redhat.com>
(cherry picked from commit 528eae9)

Conflicts:
	src/osd/ReplicatedPG.cc
                    code section was moved to ReplicatedPG::maybe_promote
                    in master.
Signed-off-by: Robert LeBlanc <robert.leblanc@endurance.com>

src/osd/ReplicatedPG.cc

@@ -1860,8 +1860,9 @@ bool ReplicatedPG::maybe_handle_cache(OpRequestRef op,
       if (count) {
 	// Check if in other hit sets
 	const hobject_t& oid = obc.get() ? obc->obs.oi.soid : missing_oid;
-	for (map<time_t,HitSetRef>::iterator itor = agent_state->hit_set_map.begin();
-	     itor != agent_state->hit_set_map.end();
+	for (map<time_t,HitSetRef>::reverse_iterator itor =
+	       agent_state->hit_set_map.rbegin();
+	     itor != agent_state->hit_set_map.rend();
 	     ++itor) {
 	  if (!itor->second->contains(oid)) {
 	    break;