rgw: allow fastcgi idle timeout to be adjusted

Signed-off-by: Sage Weil <sage@inktank.com>
Merge pull request #230 from ceph/wip-7702

rgw: allow fastcgi idle timeout to be adjusted

Reviewed-by: Yehuda Sadeh <yehuda@inktank.com>
Merge remote-tracking branch 'gh/firefly'