Revert "PG::init: clear rollback info for backfill as well"

Log here is already empty, need to rollback the log when we start
removal in on_removal().

This reverts commit 1e69ff2f3c.

src/osd/PG.cc

@@ -2418,11 +2418,6 @@ void PG::init(
     dout(10) << __func__ << ": Setting backfill" << dendl;
     info.last_backfill = hobject_t();
     info.last_complete = info.last_update;
-
-    PGLogEntryHandler rollbacker;
-    pg_log_t empty;
-    pg_log.claim_log_and_clear_rollback_info(empty, &rollbacker);
-    rollbacker.apply(this, t);
     pg_log.mark_log_for_rewrite();
   }