juju debug-log is broken

A recent commit 7fc118f015d8480dfad7831788e4b8c0432205e8 made this change in rsyslog/worker.go:

 return &tls.Config{
  RootCAs: cert,
+ ServerName: "juju-rsyslog",
 }, nil

Trouble is, it breaks rsyslog on worker nodes, and hence debug-log is broken, because rsyslog cannot connect back to the state server:
eg, on an EC2 deployment

2014-11-03 02:56:34 ERROR juju.worker runner.go:219 exited "rsyslog": x509: certificate is valid for ip-10-46-174-79.ec2.internal, not juju-rsyslog

Removing the ServerName fixed everything up again. But the change says that:

// composeTLS generates a new client certificate for connecting to the rsyslog server.
// We explicitly set the ServerName field, this ensures that even if we are connecting
// via an IP address and are using an old certificate (pre 1.20.9), we can still
// successfully connect.

So it seems by removing the ServerName, rsyslog to old state servers will break? Either way, it's broken and needs to be fixed.