Always process movement for vehicles and passengers. Fixes BUKKIT-4142

As an optimization we don't do any movement processing on entities that
have not moved. However, players in minecarts trigger this condition when
the minecart is moving on its own. This causes issues with things that rely
on player collision like tripwires. To correct this and any future related
issues we always handle movement for passengers and their vehicles even
if one of the two hasn't moved since they are linked.