rgw: don't log system requests in usage log

Fixes: 6889
System requets should not be logged in the usage log.

Signed-off-by: Yehuda Sadeh <yehuda@inktank.com>
(cherry picked from commit 42ef8ba543c7bf13c5aa3b6b4deaaf8a0f9c58b6)
rgw: fix swift range response

Fixes: #7099
Backport: dumpling
The range response header was broken in swift.

Reported-by: Julien Calvet <julien.calvet@neurea.com>
Signed-off-by: Yehuda Sadeh <yehuda@inktank.com>
(cherry picked from commit 0427f61544529ab4e0792b6afbb23379fe722de1)