Allow conntrack-related packets at start of mangle PREROUTING chain
Allow conntrack-related packets at start of mangle PREROUTING chain

Also use the configured allow action for mangle table, instead of
hardcoding ACCEPT.

neiljerram/felix,neiljerram/felix,Metaswitch/calico,Metaswitch/calico,neiljerram/felix,neiljerram/felix