[neutron2snabb] Disable security group config temporarily.
Merge pull request #253 from eugeneia/neutron2snabb_disable_secgroups

[neutron2snabb] Disable security group config temporarily
generates more than one ingress rule per port
do egress filters
install egress filter
remove 'TODO' comment line
first draft of stateful filters
implement CLOCK_MONOTONIC_COARSE for fast time-checking
use simple old/new/swap expiration algorithm