virXMLParseHelper: Rework error reporting

virXMLParseHelper: Rework error reporting

Move the reporting of parsing error on the error path of the parser as
other code paths report their own errors already.

Additionally prefer printing the 'url' as document name if provided
instead of "[inline data]" as that usually gives a better hint at least
which kind of XML is being parsed.

Signed-off-by: Peter Krempa <pkrempa@redhat.com>
Reviewed-by: Tim Wiederhake <twiederh@redhat.com>