In confirm close dialog, remove 'close current tab' option

Summary:
When there is only one tab and a process is running, remove the
'close current tab' option when attempting to close Konsole.

Test Plan:

1. Open Konsole (assuming you have not check 'Do not ask again')
2. Start any process (ie top)
3. Try to close Konsole

Should only be 2 options, 'Close window' and 'Cancel'

Reviewers: Konsole, hindenburg

Reviewed By: Konsole, hindenburg

Subscribers: hindenburg, ngraham, konsole-devel

Tags: Konsole

Differential Revision: https://phabricator.kde.org/D23146