pfSense

Do not use reference to avoid losing data

Ignore upgrade_167_to_168() when upgrade_166_to_167() runs, they are both the same

Always run additional_config_upgrade() and do it after config is written

Each item in additional_config_upgrade() must write config after changing it

Detect old workarounds in config upgrade and deal with them

Bring upgrade_166_to_167() to 2.3 world

Move workaround used to enable pkg metadata update cronjob to a generic mechanism

Check if specific config upgrade code already ran and skip it

Add a function to be called every time convert_config() runs

Revert config version to 15.8 and remove upgrade script

(cherry picked from commit d800d0f5babe2f6d7bb9a7de8afa709c28e930df)