sheep: remove object list cache of ledger when removed from store

Each object list cache should be removed when it is removed from
object store. Inode and data ones are done so by peer_remove_obj.
However, ledger objects are not so by peer_decref_object, and
remaining cache leads to unnecessary recovery trial and error log.

This commit lets sheep remove object list cache of ledger when it is
removed from store.

Fix #341

Signed-off-by: Takashi Menjo <menjo.takashi@lab.ntt.co.jp>
(cherry picked from commit 254730a)

sheep/ops.c

@@ -1201,6 +1201,7 @@ int peer_decref_object(struct request *req)
 
 		/* reclaim object */
 		if (exist) {
+			objlist_cache_remove(ledger_oid);
 			ret = sd_store->remove_object(ledger_oid, -1);
 			if (ret != SD_RES_SUCCESS) {
 				sd_err("error %s", sd_strerror(ret));