fix config loading
fix typos
set config to None
log if control file is not found
use correct control file name
open control file for writing
if $common_name is empty, use $username (user supplied instead of cert-enforced)
Note: openvpn or prior scripts have to validate the username during authentication.
The openvpn-netfilter script will not validate the username, it accepts anything that is given and assumes the user is
properly authenticated.
Update netfilter_openvpn.c

don't overwrite what openvpn does with sig_chld. this breaks waitpid() for subsequent scripts, for example.

just make sure the called script always dies properly, else deal with zombies.
Proper handling of sigchld.