switch_to_interface() to start interface if not connected

Two places currently have switch-to-or-start-interface logic.
Put that common logic into switch_to_interface().

lib/network.py

@@ -359,15 +359,18 @@ class Network(util.DaemonThread):
             self.switch_to_interface(server)
 
     def switch_to_interface(self, server):
-        '''Switch to server as our interface, it must be in self.interfaces'''
-        assert server in self.interfaces
-        self.print_error("switching to", server)
-        self.interface = self.interfaces[server]
+        '''Switch to server as our interface.  If not already connected, start a
+        connection - we will switch on receipt of the connection notification'''
         self.default_server = server
-        self.send_subscriptions()
-        self.set_status('connected')
-        self.notify('updated')
-
+        if server in self.interfaces:
+            self.print_error("switching to", server)
+            self.interface = self.interfaces[server]
+            self.send_subscriptions()
+            self.set_status('connected')
+            self.notify('updated')
+        else:
+            self.print_error("starting %s; will switch once connected" % server)
+            self.start_interface(server)
 
     def stop_interface(self):
         self.interface.stop()
@@ -384,13 +387,7 @@ class Network(util.DaemonThread):
         if self.is_connected():
             self.stop_interface()
 
-        # start interface
-        self.default_server = server
-
-        if server in self.interfaces.keys():
-            self.switch_to_interface(server)
-        else:
-            self.start_interface(server)
+        self.switch_to_interface(server)
 
 
     def add_recent_server(self, i):
@@ -500,17 +497,12 @@ class Network(util.DaemonThread):
             if self.config.get('auto_cycle'):
                 self.switch_to_random_interface()
             else:
-                if self.default_server in self.interfaces.keys():
-                    self.switch_to_interface(self.default_server)
+                if self.default_server in self.disconnected_servers:
+                    if now - self.server_retry_time > SERVER_RETRY_INTERVAL:
+                        self.disconnected_servers.remove(self.default_server)
+                        self.server_retry_time = now
                 else:
-                    if self.default_server in self.disconnected_servers:
-                        if now - self.server_retry_time > SERVER_RETRY_INTERVAL:
-                            self.disconnected_servers.remove(self.default_server)
-                            self.server_retry_time = now
-                    else:
-                        if self.default_server not in self.pending_servers:
-                            self.print_error("forcing reconnection")
-                            self.start_interface(self.default_server)
+                    self.switch_to_interface(self.default_server)
 
     def run(self):
         while self.is_running():