Purge ubuntu getting started guide of old info

The ubuntu getting started guide has not been maintained, and
most likely no longer works.  We should point people to Debian/Ubuntu
docs when they exist, or the devstack getting started guide.

Change-Id: I27a12b5366739ffcad459706c0712882b89abd2f
Closes-Bug: #1182428
Merge "Purge ubuntu getting started guide of old info"