This moves the dialog type overriding that gnome-software uses to bring
up restartInstallDialogContent from _sync() to OpenAsync(), in order to
ensure the type is overridden early enough to show the correct buttons.
While at this, make sure the & symbol in the button's label is escaped
to avoid runtime warnings, now that the label actually gets used.
https://bugzilla.gnome.org/show_bug.cgi?id=722898
7551e134da