Scanner should distinguish between network and server errors when uploading report

The scanner has a generic error message when the upload report fails, with the format "Failed to upload report - [...]".

That message is misleading in the cases when the upload actually succeeded (from the network perspective) but the WS failed to process it and returned an error status code.

In that case, the error should point to the server logs, such as:

"Server failed to process the report. Please check server logs. [...]".