rgw: when setting bucket metadata key, don't override placement

Bucket placement also contains data and index pools locations in
the source zone. However, we might be applying it on a different
zone, so we need to be careful not to use the source location here.
We generate a new placement if a new bucket is detected, otherwise
we keep the old one.

Signed-off-by: Yehuda Sadeh <yehuda@inktank.com>
rgw: multiple changes for intra-zone object copy

Signed-off-by: Yehuda Sadeh <yehuda@inktank.com>
rgw: set bucket marker and bucket obj version from master

Make sure that bucket that's created gets the same marker as
the one that the master region generated. Also, for some reason
we weren't passing in the metadata obj version for the bucket.

Signed-off-by: Yehuda Sadeh <yehuda@inktank.com>