[mod_accesslog] do not double-count hdr len in %I
[mod_accesslog] do not double-count hdr len in %I

do not double-count HTTP/2 stream request header len in %I

(overlooked and should have been adjusted in 8fc8ab89)

lighttpd/lighttpd1.4,gstrauss/lighttpd1.4,lighttpd/lighttpd1.4,gstrauss/lighttpd1.4,lighttpd/lighttpd1.4,lighttpd/lighttpd1.4,gstrauss/lighttpd1.4,gstrauss/lighttpd1.4,lighttpd/lighttpd1.4,lighttpd/lighttpd1.4,gstrauss/lighttpd1.4,gstrauss/lighttpd1.4