Zone file import failes to show errors

I ran into an issue with the DNS zone import ... and was wondering why I saw no errors.

After some digging I found that the http request did return html for an error message, it just never got loaded into the DOM.

After debugging further I found that while submitForm replaces the content in $('#pageContent') submitUploadFormdoes it differently and only extracts a few elements (#errorMsg and #OKMsg)

I'll add a MR to restore the #errorMsg.