BUG/MEDIUM: http: switch the request channel to no-delay once done.

BUG/MEDIUM: http: switch the request channel to no-delay once done.

There's an issue when sending POST data that came in a second packet,
the CF_NEVER_WAIT flag is not always set on the request channel, while
the server is waiting for the request. We must always set this flag in
this case since we're not going to shut down after sending, contrary
to the response side.

Note that option http-no-delay works around this issue.

Reproducer :

listen  px
        mode http
        timeout client 10s
        timeout server 5s
        timeout connect 3s
        option http-server-close
        #option http-no-delay
        bind :8001
        server s1 127.0.0.1:8003

$ (printf "POST / HTTP/1.1\r\nTransfer-encoding: chunked\r\n\r\n"; sleep 0.01; printf "10\r\nAZERTYUIOPQSDFGH\r\n0\r\n\r\n") | nc6 0 8001

Before this fix :

12:03:31.946763 epoll_wait(3, {{EPOLLIN, {u32=5, u64=5}}}, 200, 1000) = 1
12:03:32.634175 accept4(5, {sa_family=AF_INET, sin_port=htons(53849), sin_addr=inet_addr("127.0.0.1")}, [16], SOCK_NONBLOCK) = 6
12:03:32.634318 setsockopt(6, SOL_TCP, TCP_NODELAY, [1], 4) = 0
12:03:32.634434 accept4(5, 0x7ffccfbb2cf0, [128], SOCK_NONBLOCK) = -1 EAGAIN (Resource temporarily unavailable)
12:03:32.634574 recvfrom(6, "POST / HTTP/1.1\r\nTransfer-encodi"..., 8192, 0, NULL, NULL) = 47
12:03:32.634809 setsockopt(6, SOL_TCP, TCP_QUICKACK, [1], 4) = 0
12:03:32.634952 socket(PF_INET, SOCK_STREAM, IPPROTO_TCP) = 7
12:03:32.635031 fcntl(7, F_SETFL, O_RDONLY|O_NONBLOCK) = 0
12:03:32.635089 setsockopt(7, SOL_TCP, TCP_NODELAY, [1], 4) = 0
12:03:32.635153 connect(7, {sa_family=AF_INET, sin_port=htons(8003), sin_addr=inet_addr("127.0.0.1")}, 16) = -1 EINPROGRESS (Operation now in progress)
12:03:32.635315 epoll_wait(3, {}, 200, 0) = 0
12:03:32.635394 sendto(7, "POST / HTTP/1.1\r\nTransfer-encodi"..., 66, MSG_DONTWAIT|MSG_NOSIGNAL, NULL, 0) = 66
12:03:32.635527 recvfrom(6, 0x7f0224e66024, 8192, 0, 0, 0) = -1 EAGAIN (Resource temporarily unavailable)
12:03:32.635651 epoll_ctl(3, EPOLL_CTL_ADD, 6, {EPOLLIN|0x2000, {u32=6, u64=6}}) = 0
12:03:32.635782 epoll_wait(3, {}, 200, 0) = 0
12:03:32.635842 recvfrom(7, 0x7f0224e66024, 8192, 0, 0, 0) = -1 EAGAIN (Resource temporarily unavailable)
12:03:32.635924 epoll_ctl(3, EPOLL_CTL_ADD, 7, {EPOLLIN|0x2000, {u32=7, u64=7}}) = 0
12:03:32.636027 epoll_wait(3, {{EPOLLIN, {u32=6, u64=6}}}, 200, 1000) = 1
12:03:32.644892 recvfrom(6, "10\r\nAZERTYUIOPQSDFGH\r\n0\r\n\r\n", 8192, 0, NULL, NULL) = 27
12:03:32.645016 epoll_wait(3, {}, 200, 0) = 0
12:03:32.645105 sendto(7, "10\r\nAZERTYUIOPQSDFGH\r\n0\r\n\r\n", 27, MSG_DONTWAIT|MSG_NOSIGNAL|MSG_MORE, NULL, 0) = 27

After the fix :

11:59:12.538617 connect(7, {sa_family=AF_INET, sin_port=htons(8003), sin_addr=inet_addr("127.0.0.1")}, 16) = -1 EINPROGRESS (Operation now in progress)
11:59:12.538787 epoll_wait(3, {}, 200, 0) = 0
11:59:12.538867 sendto(7, "POST / HTTP/1.1\r\nTransfer-encodi"..., 66, MSG_DONTWAIT|MSG_NOSIGNAL, NULL, 0) = 66
11:59:12.539031 recvfrom(6, 0x7f832ce45024, 8192, 0, 0, 0) = -1 EAGAIN (Resource temporarily unavailable)
11:59:12.539161 epoll_ctl(3, EPOLL_CTL_ADD, 6, {EPOLLIN|0x2000, {u32=6, u64=6}}) = 0
11:59:12.539259 epoll_wait(3, {}, 200, 0) = 0
11:59:12.539337 recvfrom(7, 0x7f832ce45024, 8192, 0, 0, 0) = -1 EAGAIN (Resource temporarily unavailable)
11:59:12.539421 epoll_ctl(3, EPOLL_CTL_ADD, 7, {EPOLLIN|0x2000, {u32=7, u64=7}}) = 0
11:59:12.539499 epoll_wait(3, {{EPOLLIN, {u32=6, u64=6}}}, 200, 1000) = 1
11:59:12.548519 recvfrom(6, "10\r\nAZERTYUIOPQSDFGH\r\n0\r\n\r\n", 8192, 0, NULL, NULL) = 27
11:59:12.548844 epoll_wait(3, {}, 200, 0) = 0
11:59:12.549012 sendto(7, "10\r\nAZERTYUIOPQSDFGH\r\n0\r\n\r\n", 27, MSG_DONTWAIT|MSG_NOSIGNAL, NULL, 0) = 27
11:59:12.549454 epoll_wait(3, {}, 200, 1000) = 0

This fix must be backported to 1.6, 1.5 and 1.4.