agfs-keygen needs to specify port

[robojeb]

agfs-keygen does not have a port argument. This is fine under the current situation if all agfs-servers listen on the same port but if we allow servers to listen on different ports we will need to specify that port in the key-file so the client can successfully connect.

[MarkCMann]

AgFS-keygen now has a port argument that it uses correctly to create a key for the server that will listen on the given port.