disabling IPv6 on setup not idempotent

[petiepooo]

securityonion/setup/so-functions

Line 939 in 12762e0

} >> /etc/sysctl.conf

These lines are added each time so-setup is run, meaning they are duplicated when so-setup is run multiple times. There should probably be a check for their presence first before adding them.

Alternatively, at least on debian/ubuntu systems, it's best practice to create a new file in the drop-in directory at /etc/sysctl.d/ instead of modifying the actual sysctl.conf file itself. That would prevent the need to check for presence first.