t5537: move http tests out to t5539

start_httpd is supposed to be at the beginning of the test file, not
the middle of it. The "test_seq" line in "no shallow lines.." test is
updated to compensate missing refs that are there in t5537, but not in
the new t5539.

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>