* Be sure we send updates to multiple clients for the same user
* Be sure we send a full contacts update on initial connection

As part of this commit, I fixed an issue where we couldn't disconnect and reconnect in tests. The first disconnect would cause the I/O future to terminate asynchronously, which caused us to sign out even though the active connection didn't belong to that future. I added a guard to ensure that we only sign out if the I/O future is associated with the current connection.