Fixes killswitch.sh not being executed due to script security

[nake90]

I was not able to connect from my local network to the open port from one of the docker containers, and while debugging I noticed that the reason was that killswitch.sh was not being executed after openvpn is up (and thus the iptables was not being set correctly).

Checking the openvpn logs I found this:

2023-06-06 14:01:18 WARNING: External program may not be called unless '--script-security 2' or higher is enabled. See --help text or man page for detailed info.
2023-06-06 14:01:18 WARNING: Failed running command (--route-up): disallowed by script-security setting
2023-06-06 14:01:18 Initialization Sequence Completed

So basically, if killswitch is set, I add --script-security 2.