display_page_message: use a flag instead of booleans
display_page_message: use a flag instead of booleans

More scalable.

https://bugzilla.gnome.org/show_bug.cgi?id=683326

Distrotech/telepathy-account-widgets,Distrotech/telepathy-account-widgets,GNOME/telepathy-account-widgets,GNOME/telepathy-account-widgets,GNOME/telepathy-account-widgets