display name created but not saved by juju for bootstrap machine.

[Heather Lanigan]

For some clouds, the instance id is very long, to simplify the `juju status` output we use a DisplayName. When bootstrapping the display name is created, but not saved for the bootstrap machine.

juju:PRIMARY> db.instanceData.find().pretty()
{
 "_id" : "da7e86c4-595b-453e-8e26-38b97f2c4e4a:0",
 "machineid" : "0",
 "instanceid" : "ocid1.instance.oc1.phx.anyhqljtniwq6sycjken42nduo56kco3tcht3mny7vmd4n6mnndk3ukhk6za",
 "display-name" : "",
 "model-uuid" : "da7e86c4-595b-453e-8e26-38b97f2c4e4a",
 "arch" : "amd64",
 "txn-revno" : NumberLong(2),
 "txn-queue" : [
  "61e831f811a9973d9e3f94c4_b889f48d"
 ]
}

All machines after bootstrap, have a display name.