Merge pull request #13035 from yehudasa/wip-18621

rgw: change default chunk size to 4MB

diff --cc src/common/config_opts.h
Simple merge

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

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

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