Fail/exit if invalid port actions are given (like the deprecated 'block')

[PherricOxide]

We should fail when parsing the configuration file if the port action is invalid instead of just defaulting to 'open'.

[PherricOxide]

It was decided to just map 'block' to 'filtered' and 'reset' to 'closed' in order for old honeyd configuration files to work properly still.