QXmppTransferManager: Close only devices which we opened.
QXmppTransferManager: Close only devices which we opened.

sendFile() method expects the device to be opened, but
QXmppTransferJob::terminate() closes the dev unconditionaly, which
breaks reusable QIODevice workflow.

Introduce a private boolean variable saying "we created this device".

olesalscheider/qxmpp,pol51/QXMPP-CMake,olesalscheider/qxmpp,Kaffeine/qxmpp,olesalscheider/qxmpp,LightZam/qxmpp,pol51/QXMPP-CMake,LightZam/qxmpp,Kaffeine/qxmpp,KangLin/qxmpp,KangLin/qxmpp,kollix/qxmpp,KangLin/qxmpp,LightZam/qxmpp,Kaffeine/qxmpp,kollix/qxmpp,pol51/QXMPP-CMake,kollix/qxmpp