RDP: replace the non-supported signal

The following 2 signals are not available in Qt5,
   QObject::connect: No such signal QWindow::clientClosed()
   QObject::connect: No such signal QWindow::clientIsEmbedded()
replace them by QProcess::finished() and QProcess::started()

Signed-off-by: AceLan Kao <acelan@acelan.idv.tw>