Merge pull request #7764 from rzarzynski/wip-rgw-etag-dlo

rgw: multiple improvements regarding etag calculation for SLO/DLO of Swift API.

Reviewed-by: Yehuda Sadeh <yehuda@redhat.com>

diff --cc src/rgw/rgw_op.cc
Simple merge

diff --cc src/rgw/rgw_op.h
Simple merge

diff --cc src/rgw/rgw_rest_s3.cc
Simple merge

diff --cc src/rgw/rgw_rest_swift.cc
Simple merge

diff --cc src/rgw/rgw_rest_swift.h
Simple merge