buffer: Change the way buffer names are created.

This mimics how the irc plugin creates buffer names.

matrix/buffer.py

@@ -683,12 +683,14 @@ class RoomBuffer(object):
         self.room = room
         self.backlog_pending = False
 
+        buffer_name = "{}.{}".format(room.room_id, server_name)
+
         # This dict remembers the connection from a user_id to the name we
         # displayed in the buffer
         self.displayed_nicks = {}
         user = shorten_sender(self.room.own_user_id)
         self.weechat_buffer = WeechatChannelBuffer(
-            room.room_id,
+            buffer_name,
             server_name,
             user
         )

matrix/utils.py

@@ -64,10 +64,12 @@ def tags_from_line_data(line_data):
 
 def create_server_buffer(server):
     # type: (MatrixServer) -> None
-    server.server_buffer = W.buffer_new(server.name, "server_buffer_cb",
+    buffer_name = "server.{}".format(server.name)
+    server.server_buffer = W.buffer_new(buffer_name, "server_buffer_cb",
                                         server.name, "", "")
 
     server_buffer_set_title(server)
+    W.buffer_set(server.server_buffer, "short_name", server.name)
     W.buffer_set(server.server_buffer, "localvar_set_type", 'server')
     W.buffer_set(
         server.server_buffer,