provider/elemental: updating presets that already exists is not working

[marzagao]

At first glance, at least how we're calling its API, Elemental Conductor doesn't seem to allow existing presets to be updated. When using the transcoding API to create/update existing presets in Elemental, we get the error Name has already been taken.

We should investigate if we're calling Elemental's API the wrong way. If not, we should mimic what Encoding.com does, which is to override the existing one.