Fix reparsing of command line arguments

If a new Konsole instance is launched via DBus (e. g. single process
mode), it re-used the QCommandLineParser each time, so each new instance
would inherit all parsed options.

Most noticeably is if you have konsole running, press Shift+F4 in
Dolphin to launch a Konsole instance in the current folder (which leads
Konsole to use a temporary profile), and then try to open a new konsole
instance outside of that, it would open in the folder from Dolphin.

REVIEW: 129217