neutron2snabb egress filters

Creates egress filter rules from Neutron config database and sets up a `packet_filter` app to enforce them.
Fixes some loop reinitialization to let the configDB -> filter rules create more than one filter rules.

I've tested this only with a fake hand-built config database.  It does handle anything i throw at it as long as it seems to comply the general syntax, but it would be great if somebody with a Neutron installation could help in more "real worlf" tests.