Minor fixes for getaddrinfo_a usage

Minor fixes for getaddrinfo_a usage

* src/process.c (Fdelete_process): Check gai_cancel return value.
That way, there’s no need to invoke gai_error.  Check gai_suspend
return value.
(Fmake_network_process): Don’t assume gai_strerror returns a UTF-8
string.  Simplify call to connect_network_socket.
(check_for_dns): Avoid unnecessary initialization of local.