Use DECSCUSR 0 to reset to default

Summary:
This isn't standardized, but matches what VTE does.

printf '\e[0 q' # reset to default

Ref. https://bugzilla.gnome.org/show_bug.cgi?id=720821 and
https://bug720821.bugzilla-attachments.gnome.org/attachment.cgi?id=291238

Reviewers: Konsole, hindenburg

Reviewed By: Konsole, hindenburg

Subscribers: hindenburg, ahmadsamir, konsole-devel, Konsole

Tags: Konsole

Differential Revision: https://phabricator.kde.org/D17266