[startkde] Fix login
The QProcess object only needs to last during the lifespan of startPlasmaSession, but it's still important that it has the lifespan of the whole method not just the one if branch before we get to the exec()
The QProcess object only needs to last during the lifespan of startPlasmaSession, but it's still important that it has the lifespan of the whole method not just the one if branch before we get to the exec()