Commit 8822256 changed the way that
Node objects are constructed from EC2Slave objects, in order to make the
Node 'name' fields more useful. It also added a field called 'instanceId'
to EC2Slave, and stopped relying on Node.getNodeName() to recover that
information. In order to provide compatibility with configurations from
before this change was made, this patch notes whether instanceId is null,
and if it is, extracts the instance ID from the Node's name.