setup-apkrepos: force install virtual package

it is tmpfs and we know it will be removed on reboot. Infact, we want
it to be removed on reboot.

setup-apkrepos.in

@@ -161,7 +161,7 @@ done
 # install alpine-mirrors if its not already there
 to_uninstall=
 if ! apk info --quiet --installed alpine-mirrors; then
-	apk add --quiet --virtual .setup-apkrepos alpine-mirrors
+	apk add --force --quiet --virtual .setup-apkrepos alpine-mirrors
 	to_uninstall=.setup-apkrepos
 fi