global: remove automatic notrack rules

global: remove automatic notrack rules

With recent Kernel versions and the introduction of the conntrack routing
cache there is no need to maintain performance hacks in userspace anymore,
so simply drop the generation of automatic -j CT --notrack rules for zones.

This also fixes some cases where traffic is not matched for zones that do
not explicitely enforce connection tracking.

Signed-off-by: Jo-Philipp Wich <jo@mein.io>