rgw/reshard: copy the index entries to dest shards.

rgw/reshard: copy the index entries to dest shards.

In logrecord state, copy inventoried index entries to dest shards
and record a log for new writting entry. In progress state, block
the writes, listing the logs written in logrecord state, then gain
corresponding index entries and copy them to dest shards.

Signed-off-by: Mingyuan Liang <liangmingyuan@baidu.com>