Discrepancy between debrief_init and multi_standalone_postgame_init

In `debrief_init`, the function calls `mission_campaign_store_goals_and_events` without storing variables at the time. Later, depending on whether the debriefing is accepted, the game may call `mission_campaign_store_variables`.

In `multi_standalone_postgame_init`, the function calls `mission_campaign_store_goals_and_events_and_variables` which stores all three. This may put the variables into the wrong state.