[UI] Calendar shown for expiring subkey doesn't get focus

Submitted by Christian Stadelmann `@genodeftest`

Link to original bug (#757238)

Description

Steps to reproduce:

open seahorse
go to your gnupg keys
open properties for your own gnupg key
go to tab "details"
press button "Expire" below "Subkeys"

A dialog will open showing a GtkDialog with a GtkCalendar. This Calendar doesn't get focus in most (but not all) cases.

Version: 3.16.x