Open sockets should not be inherited by cores

[arisu3]

Sockets in the client are opened without SOCK_CLOEXEC (cbang does not set it by default). This causes the cores to inherit open network connections that they do not need. This is unnecessary and complicates sandboxing.

$ lsof -i tcp:7396 -a -c FahCore_ -c fah-client
COMMAND      PID    USER   FD   TYPE  DEVICE SIZE/OFF NODE NAME
fah-clien 406867 fahtest    9u  IPv4 2157736      0t0  TCP localhost:7396->localhost:34940 (ESTABLISHED)
fah-clien 406867 fahtest   10u  IPv4 1803050      0t0  TCP localhost:7396 (LISTEN)
fah-clien 406867 fahtest   27u  IPv4 1803652      0t0  TCP localhost:7396->localhost:47630 (ESTABLISHED)
FahCore_2 465571 fahtest   24u  IPv4 2110072      0t0  TCP localhost:7396->localhost:33774 (CLOSE_WAIT)
FahCore_2 465571 fahtest   27u  IPv4 1803652      0t0  TCP localhost:7396->localhost:47630 (ESTABLISHED)
FahCore_a 466366 fahtest    9u  IPv4 2157736      0t0  TCP localhost:7396->localhost:34940 (ESTABLISHED)
FahCore_a 466366 fahtest   27u  IPv4 1803652      0t0  TCP localhost:7396->localhost:47630 (ESTABLISHED)