MEDIUM: actions: add new flag ACT_FLAG_FINAL to notify about last call

MEDIUM: actions: add new flag ACT_FLAG_FINAL to notify about last call

This new flag indicates to a custom action that it must not yield because
it will not be called anymore. This addresses an issue introduced by commit
bc4c1ac ("MEDIUM: http/tcp: permit to resume http and tcp custom actions"),
which made it possible to yield even after the last call and causes Lua
actions not to be stopped when the session closes. Note that the Lua issue
is not fixed yet at this point. Also only TCP rules were handled, for now
HTTP rules continue to let the action yield since we don't know whether or
not it is a final call.