Allow degraded/misplaced writes (for better performance)

src/osd/osd_peering_pg.h

@@ -29,6 +29,7 @@ struct pg_osd_set_state_t
     std::vector<osd_num_t> read_target;
     // full OSD set including additional OSDs where the object is misplaced
     pg_osd_set_t osd_set;
+    bool has_extra = false;
     uint64_t state = 0;
     uint64_t object_count = 0;
     uint64_t ref_count = 0;