Replace GFSM calls with direct calls to TLS and HTTP

[ttaym]

Contributes to #755

Porting of 2eae1da

Replace GFSM calls with direct calls to TLS and HTTP handlers
 on low level networking layers.

GFSM was designed to build graphs of network protocols FSMs (this
design was inspired by FreeBSD netgraph). However, during the years
neither we nor external users have any requirements to introduce
any modules which use GFSM to hook TLS or HTTP entry code. There
are only 2 users of the mechanism for TLS and HTTP for now:
1. TLS -> HTTP protocols handling
2. HTTP limits (the frang module)

This patch replaces GFSM calls with direct calls to
tfw_http_req_process(), tfw_tls_msg_process() and frang_tls_handler()
in following paths:
1. sync sockets -> TLS
2. sync sockets -> HTTP
3. TLS -> HTTP
4. TLS -> Frang

As the result the function tfw_connection_recv() was eliminated.
Now the code is simpler and has lower overhead.

We still might need GFSM for the user-space requests handling (#77)
and Tempesta Language (#102).

Based-on-patch-by: Alexander K ak@tempesta-tech.com
Signed-off-by: Aleksey Mikhaylov aym@tempesta-tech.com

[krizhanovsky]

LGTM

[ttaym]

I manually test patch on VPS instance with:

~$ curl -vik --resolve debian.tempesta:443:44.93.154.134 https://debian.tempesta/

And config:

listen 443 proto=https;

srv_group default {
    server 127.0.0.1:8000 conns_n=4;
}

vhost debian.tempesta {
    proxy_pass default;
    tls_certificate     /root/cert.pem;
    tls_certificate_key /root/privkey.pem;
}

cache 1;
cache_fulfill * *;

block_action attack reply;

http_chain {
    -> debian.tempesta;
}

Connection established and https request served.