This commit moves the check against server->input_mode from the callers
of desktop_focus_view() into desktop_focus_view() itself. This
eliminates code duplications and makes it harder to mess up the window
stacking order while window switching.
I also added the same check in view_minimize() so that minimize requests
from panels never messes up the window stacking order (I think only this
should be described in the release note).
This fixes a bug that output_enter events are not sent when a Slack
window running in background is re-mapped, which caused missing taskbar
items in Waybar when it's configured to show windows per output.
