Fix various roster count issues

disconnections not clearing the number of connected contacts, leading to
an ever-increasing count, and roster count not always being setup

src/core/handlers.py

@@ -748,6 +748,7 @@ def on_roster_update(self, iq):
                 del roster[jid]
             else:
                 roster.update_contact_groups(jid)
+    roster.update_size()
     if isinstance(self.current_tab(), tabs.RosterInfoTab):
         self.refresh_window()
 
@@ -936,6 +937,7 @@ def on_disconnected(self, event):
     """
     When we are disconnected from remote server
     """
+    roster.connected = 0
     # Stop the ping plugin. It would try to send stanza on regular basis
     self.xmpp.plugin['xep_0199'].disable_keepalive()
     roster.modified()

src/roster.py

@@ -149,9 +149,14 @@ class Roster(object):
             contact = self.get_and_set(key)
             if key != self.jid and (contact and self.exists(contact)):
                 l.append(key)
-        self.length = len(l)
+        self.update_size(l)
         return l
 
+    def update_size(self, jids=None):
+        if jids is None:
+            jids = self.jids()
+        self.length = len(jids)
+
     def get_contacts(self):
         """
         Return a list of all the contacts