Fix EZP-23739: Files uploaded with multiupload will be download with the...

... wrong Content-Type

Files uploaded with multiupload are saved internally without suffix. This means they are downloaded as application/octet-stream which I assume is the default. Since the mimedata already contains the suffix, the patch simply adds it to the eZHTTPFile::store call, as it is done in eZBinaryFileType::fetchObjectAttributeHTTPInput() for example.

https://jira.ez.no/browse/EZP-23739