sld does not get replaced when uploading

[uniomni]

When uploading a layer a second time with a different sld file, it doesn't get updated.
This was a discussion that was had a while ago (A, B and C options) on the geonode mailing list.
From memory it was decided to leave the sld be as default (which is what we are now seeing) but that it shouldn't be too hard to change that behaviour to one where both data and metadata such as styling gets overwritten