Notifier plugin fix

- NotifyOSD doesn't like too many notification objects in a queue, so
just create one on init and update its contents if there is a new
notification

src/plugins/notification_notify2.py

@@ -6,8 +6,10 @@ from gi.repository import Notify
 
 Notify.init('pybitmessage')
 
-
 def connect_plugin(title, subtitle, category, label, icon):
     if not icon:
         icon = 'mail-message-new' if category == 2 else 'pybitmessage'
-    Notify.Notification.new(title, subtitle, icon).show()
+    connect_plugin.notification.update(title, subtitle, icon)
+    connect_plugin.notification.show.show()
+
+connect_plugin.notification = Notify.Notification.new("Init", "Init")