Prefer to set current mode in resolution combobox
Summary:
Preferred resolution may be lower than current resolution (e.g. on KVM),
in this case it will be selected in the combobox instead of current
resolution. Select current resolution if it's available.
Reviewers: Plasma, davidedmundson
Reviewed By: Plasma, davidedmundson
Subscribers: davidedmundson, plasma-devel
Tags: Plasma
Differential Revision: https://phabricator.kde.org/D16400