Wrong variable name used for finding a state variable in RulesAction::executeCallback()

If I'm not mistaken, the attached patch fixes a problem where you derived a variable name for finding an action's parameter in the state but then used the name of the parameter instead of the variable. I found this issue when creating a user account, fiddling with it, and saving it. Because I changed the name of the provided variable from entity_created to account_created, it wasn't finding it in subsequent actions.