[httpclient] connect to QNetworkReply::uploadProgress() immediately

Slot handleAuthenticationRequired() may not be called at all.
[httpclient] remove m_httpError flag

It's enough to set m_reply to zero in order to indicate an error.
[httpclient] remove m_userAborted flag

It's enough to set m_reply to zero in order to indicate an aborted
transaction.
[httpclient] use parent-child relationship with the private class
[httpclient] cancel a HTTP request if not connected within 2 minutes
[httpclient] avoid division by zero in handleUploadProgress()
Incremented version