The only excess contribution that you could have returned to you by the due date of your 2017 tax return is a new excess contribution made for 2017. You are not permitted to treat an old (2016) excess contribution as a new excess contribution. The only amounts that can be treated as new excess contributions for 2017 is new money contributed for 2017.
You also cannot cause a new contribution that is not an excess contribution on its own to be an excess contribution by application of a prior-year excess. You can only apply a prior-year excess as a current-year excess if you have not yet maxed out your 2017 HSA contribution limit.
