Fix bug: SIGTERM(15) is larger than SIGKILL(9)
rewrite is_network_up in terms of getaddrinfo

is_network_up was failing to connect and gethostbyname is deprecated, so
I rewrote it using getaddrinfo instead.
Several changes here, see below:

1. chkport is now a string, since getaddrinfo expects service(port) as a string
2. interval check time wasn't implemented, it was checking every cycle
3. do_exit wasn't always stopping vpnc, so run stop_cmd explicity before exiting
4. do_restart stops and starts since vpnc won't start if another instance is running
  4a. There was a bug where stop wasn't getting called before start, so do it in the same if