This imports the "launch instance" end user guide docs from
the openstack-manuals repo. As part of the docs migration
in Pike, these were forgotten. The copied contents come from
the stable/ocata branch of openstack-manuals, and therefore
likely need some updating, but that could be done in follow up
changes. This is an initial import to (1) publish the content
again somewhere and (2) fix broken links in the cinder docs
for booting from volume.
Change-Id: Ie039322660fd0e2e0403843448379b78114c425b
Partial-Bug: #1714017
Related-Bug: #1711267
4ed5e81ee0