made the connection handshaking more efficient

Ignore-this: 12bf9c118c11a2db21ccadf51a0f9cd3

There was a bug where too many connection requests were sent when the users are on a local
network and a greeter is used.

Also the ping was inefficient anyway and there were too many back and forths...

darcs-hash:20130401033207-c21fe-8e05fe03c2e0ee2dc2bd60bdfd62afc6eb23bad7