Remove references to tty-linux

The Cirros qcow2 image has been used to create a glance image, reflect
this change in the `nova image-list` output.

Cherry-picked from https://review.openstack.org/34493

Change-Id: I1f7e7b84f3cfbcc2c4b404ce2ae14c66a169ed59
Merge "Remove references to tty-linux" into stable/grizzly