Transfer command doesn't check if player is already connected

When you are trying to use the transfer command it does not check if the player is already in that server.

How to reproduce the issue:

• Make two dedicated servers.
• Open the server.properties file, and change the server-port to 25566.
• Start the servers.
• Connect to it, and type this command: /transfer localhost 25566
• Once you are connected to the server, type the same command.
• Notice that you can connect multiple times to the same ip, same port.

Expected Behaviour:
There should be a message in chat that says "You are already connected to this server." which would prevent the player to join twice to the same server.

Actual Behaviour:
The player can connect to the same exact server multiple times even if they are there.