$ juju ssh ubuntu-lxc/0 sudo -u ubuntu lsb_release -cs
Warning: Permanently added '10.96.1.13' (ECDSA) to the list of known hosts.
Warning: Permanently added '10.96.1.195' (ECDSA) to the list of known hosts.
sudo: unable to resolve host juju-machine-1-lxc-0
trusty
Connection to 10.96.1.195 closed.
$
Still happens with trusty:
$ juju ssh ubuntu-lxc/0 sudo -u ubuntu lsb_release -cs 1-lxc-0
Warning: Permanently added '10.96.1.13' (ECDSA) to the list of known hosts.
Warning: Permanently added '10.96.1.195' (ECDSA) to the list of known hosts.
sudo: unable to resolve host juju-machine-
trusty
Connection to 10.96.1.195 closed.
$
This was with juju 1.19.3